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Aromatic plants have played key roles in the lives of tribal peoples living in the Himalaya by providing products for both food and medicine. This review presents a summary of aromatic medicinal plants from the Indian Himalaya, Nepal, and Bhutan, focusing on plant species for which volatile compositions have been described. The review summarizes 116 aromatic plant species distributed over 26 families.
The Himalya Center of Plant Diversity  is a narrow band of biodiversity lying on the southern margin of the Himalayas, the world’s highest mountain range with elevations exceeding 8000 m. The plant diversity of this region is defined by the monsoonal rains, up to 10,000 mm rainfall, concentrated in the summer, altitudinal zonation, consisting of tropical lowland rainforests, 100–1200 m asl, up to alpine meadows, 4800–5500 m asl. Hara and co-workers have estimated there to be around 6000 species of higher plants in Nepal, including 303 species endemic to Nepal and 1957 species restricted to the Himalayan range [2,3,4]. The Indian Himalaya is home to more than 8000 species of vascular plants  of which 1748 are known for their medicinal properties .
Higher plants have played key roles in the lives of tribal peoples living in the Himalaya by providing forest products for both food and medicine. Numerous wild and cultivated plants have been utilized as curative agents since ancient times, and medicinal plants have gained importance recently, not only as herbal medicines, but also as natural ingredients for the cosmetic industry. In this review, we summarize aromatic medicinal plants from Bhutan, Nepal, and the Indian Himalaya of Uttarakhand, Himachal Pradesh, and Jammu and Kashmir (Figure 1). We have focused the review on plant species for which volatile compositions have been described. In searching the literature (Google Scholar), we have used the keywords: essential oil, Himalaya, Bhutan, Nepal, Uttarakhand, Himachal Pradesh, and Kashmir. For essential oils from these regions that were reported in the literature, we have carried out an additional search using the plant name and the keywords, ethnobotany, ethnopharmacology.
Table 1 summarizes the aromatic medicinal plants of the Himalayan region and includes ethnopharmacological uses of the plants, essential oil compositions, and any biological activities of the essential oils. In addition, we describe in more detail some important genera and species used as aromatic medicinal plants in this region.
There are approximately 400 species of Artemisia distributed throughout temperate regions of the world, and the genus is typically characterized by aromatic shrubs and herbs . Numerous members of the genus are used as traditional medicines by indigenous cultures, and many show biological activities including antimalarial, cytotoxic, antihepatotoxic, antibacterial, antifungal and antioxidant activities . Some particularly notable members of the genus include A. absinthium L., the major component of the notorious spirit drink absinthe ; A. annua L., the efficacious antimalarial drug qinghaosu ; A. dracunculus L., the flavoring herb tarragon ; and A. tridentata Nutt., the “big sagebrush” of western North America .
In the Himalaya, 19 species of Artemisia are recognized to be medicinal herbs (A. absinthium, A. biennis, A. brevifolia, A. desertorum, A. dracunculus, A. dubia, A. gmelinii, A. indica, A. japonica, A. lacinata, A. macrocephala, A. maratima, A. moorcroftiana, A. nilagarica, A. parviflora, A. roxburghiana, A. scoparia, A. sieversiana, and A. vulgaris) [55,59], and some of these have been investigated for volatile compositions and bioactivity (see Table 1). A. dracunculus (tarragon) is used worldwide, including the Himalayan region, as a flavoring agent for food. The plant is also used ethnobotanically. Native peoples in the Nubra valley (Kashmir) , Kibber Wildlife Sanctuary (Himachal Pradesh) , and the Lahaul Valley (Himachal Pradesh)  use a paste from the leaves to treat wounds on the legs of donkeys and yaks; an extract of the whole plant is used to relieve toothache, reduce fever, and as a treatment for dysentery, intestinal worms, and stomachache. A. dracunculus from the Himalayas is a rich source of the diacetylene capillene and the monoterpene (Z)-β-ocimene [36,37,41], and is markedly different from “French tarragon”, which is dominated by estragole (up to 74%), or “Russian tarragon”, which is dominated by elemicin (up to 57%), or other cultivars of A. dracunculus .
The leaf juice of A. dubia is used by villagers in the Dolpa district of Nepal  and the Newar community of Kathmandu, Nepal , as an antiseptic to cure cuts and wounds and the leaf extracts are used as pesticides. The essential oil of A. dubia was shown to be rich in chrysanthenone (29.0%), coumarins (18.3%), and camphor (16.4%) . Although the leaf oil showed in vitro cytotoxic activity against MCF-7 human breast tumor cells and antifungal activity against Aspergillus niger, it was inactive against the bacteria Bacillus cereus, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa . Thus, the antiseptic qualities of A. dubia must be due to non-volatile components in the plant.
In the Humla district of northwestern Nepal, the whole fresh plant of A. gmelinii is ground into a paste an applied externally to cure headache, boils, and pimples . The essential oils from the aerial parts of A. gmelinii from Himalayan India are dominated by artemisia ketone and 1,8-cineole [45,46]. Neither of these compounds, however, are notably antibacterial (B. cereus, S. aureus, E. coli, P. aeruginosa) or antifungal (Candida albicans, A. niger) .
The essential oil composition of A. indica has shown wide variation. The leaf essential oil from Nepal was dominated by ascaridole (15.4%), isoascaridole (9.9%), trans-p-mentha-2,8-dien-1-ol (9.7%), and trans-verbenol (8.4%) . Conversely, the essential oil from the aerial parts of a sample from Uttarakhand, India was rich in davanone (30.8%), β-pinene (15.3%), and germacrene D (5.8%) , while the aerial parts essential oil from a sample collected from Kashmir was dominated by artemisia ketone (42.1%), germacrene B (8.6%), and borneol (6.1%) . The oil from Kashmir was screened for antimicrobial activity and showed extraordinary activity against S. aureus and Penicillium chrysogenum (MIC = 16 μg/mL). The Kashmir oil also showed remarkable cytotoxic activity against THP-1 (leukemia), A-549 (lung), HEP-2 (liver) and Caco-2 (colon) human tumor cells. The Nepali A. indica oil showed neither antibacterial (B. cereus, S. aureus, E. coli, P. aeruginosa), antifungal (A. niger), nor cytotoxic (MCF-7 breast tumor) activities . In Nepal, the leaves are used to make a paste that is applied to cuts and wounds [11,12], while the juice of the plant is used to treat indigestion .
In the Garhwal Himalaya, Uttarakhand, the leaves of Artemisia japonica are used as an incense and insecticide  and in ethnoveterinary medicine the plant is used as a treatment for internal parasites (e.g., round worm) . In northern Pakistan, the leaf extract is used to treat malaria while a paste of the leaves is applied externally to treat skin diseases . The essential oil from the aerial parts of A. japonica collected from Milam glacier (Uttarakhand), India, was dominated by the monoterpenoids linalool (27.5%), (E)-β-ocimene (6.5%), 1,8-cineole (5.5%), and (Z)-β-ocimene (5.5%), along with germacrene D (11.2%) . In contrast, a sample of A. japonica from southern India (Munmar, Kerala) was rich in sesquiterpene hydrocarbons: Spathulenol (12%), germacrene D (7.5%), β-elemene (2.8%), β-caryophyllene (2.4%) .
Artemisia maritima is used by several Himalayan peoples to treat stomach problems and for expelling intestinal worms [50,182,308]. Mathela and co-workers  found A. maritima essential oil from Malari (Garhwal region, India) to be rich in α-thujone (63.3%), sabinene (7.8%), and 1,8-cineole (6.5%), while 1,8-cineole and chrystanthenone dominated the essential oils from Himachal Pradesh  and Chamoli (Garhwal region, India) . Camphor was the dominant monoterpenoid (44.4%) in an essential oil sample from Lahaul-Spiti (Hamachal Pradesh, India) , which was screened for antimicrobial activity (S. aureus, E. coli, S. abony, P. aeruginosa, C. albicans), but was found to be inactive. Commercial A. maritima oil from Pakistan was also rich in 1,8-cineole (41.1%) and camphor (20.3%) . α-Thujone has shown anthelmintic activity , and high concentrations of α-thujone in some A. maritima essential oils likely account for the ethnopharmacological use of this plant to expel intestinal parasites. The compound is a potent neurotoxin and modulator of the GABA-gated chloride channel, however . Conversely, camphor has been shown not have anthelmintic activity , but the compound is toxic to humans and ingestion may cause seizures [313,314]. 1,8-Cineole has been shown to inhibit castor oil-induced diarrhea in rats , prevent ethanol-induced gastric injury in rats , and attenuate trinitrobenzene sulfonic acid-induced colitis in rats , and so this compound may be an important component in the traditional use of 1,8-cineole-containing herbal medicines for stomach problems.
Artemisia nilagirica is widely found in the hilly areas of northern India, where it is used as an insecticide . A. nilagirica essential oil compositions have shown altitudinal variation. Badoni and co-workers  found that A. nilagririca from lower altitudes in Uttarakhand (500 m asl) contained α-thujone (36.9%) as the major component, the oil from intermediate elevation (1200 m asl) had mequinyl p-nitrobenzoate (22.1%), cadina-1,4-diene (17.7%), and β-eudesmol (12.4%) as the major components, and the sample from higher elevation (2000 m asl) had linalool (32.5%) and isopulegyl acetate (20.7%) as the major components. Haider and co-workers , working in Himachal Pradesh, observed a similar effect, albeit with very different composition. A. nilagririca from lower altitudes (Mandi, 1044 m asl) contained caryophyllene oxide (28.6%) as the major component, the oil from intermediate elevation (Manali, 2050 m asl) had borneol (35.8%) as the major component, and the sample from higher elevation (Shimla, 2210 m asl) was dominated by camphor (46.9%).
The A. nilagirica essential oil from Himachal Pradesh [major components: camphor (12.6%), artemisia ketone (10.2%), caryophyllene oxide (7.4%), borneol (5.3%)] showed antifungal activity against the plant pathogenic fungi Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides, but did not show antimicrobial activity against S. aureus, E. coli, S. abony, P. aeruginosa, or C. albicans . Similarly, the α-thujone-rich essential oil from Uttarakhand was active against plant pathogenic fungi Rhizoctonia solani, Sclerotium rolfsii, and Macrophomina phaseolina . Another essential oil sample from Uttarakhand [major components: linalool (16.3%), α-thujone (13.9%), β-caryophyllene (7.5%), germacrene D (7.1%)] did show notable antibacterial activity against S. aureus and P. aeruginosa with MIC values of 6.25 and 12.5 μg/mL, respectively . Traditional medical practitioners in Darjeeling, West Bengal, India, chew shoots of the plant to treat oral ulcers and apply crushed leaves to the forehead for dizziness and headaches . Inhabitants of the Parvati valley, Himachal Pradesh, India, make a paste from the leaves and apply it cuts and wounds to check bleeding . The antimicrobial activities of A. nilagrica (see above) are consistent with the traditional uses of the plant for wounds and ulcers.
Artemisia parviflora is widely distributed in the Himalayas between about 900 and 3500 m asl . In the traditional medicine of the Kumaun Himalaya, the leaves of A. parviflora are used to treat skin diseases, burns, cuts, and wounds, while the volatiles from the plant are used to repel insects . The indigenous peoples of Jammu and Kashmir (India) use A. parviflora as a diuretic and to treat gynecological disorders . The plant is also used in ethnoveterinary medicine as an anthelmintic; a decoction of the leaves and buds of the plant are given to stock animals (e.g., horses, mules, sheep, and buffaloes) for round worm . The plant is also used as a fodder plant in mid-altitude rangelands of Uttarakhand . The essential oil from the aerial parts of A. parviflora collected from Pauri, Pauri Garhwal (Uttarakhand, India) was found to contain β-caryophyllene (15.3%), germacrene D (14.7%), camphor (11.4%), artemisia ketone (7.8%), and 1,8-cineole (5.8%) . There are apparently no reports on the bioactivities of Himalayan A. parviflora essential oil, but the oil from southern India has shown antifungal activity against Candida and Cryptococcus species .
People living in the Kedarnath Wildlife Sanctuary in the western Himalaya of Chamoli-Rudraprayag (Uttarakhand), India, use an extract of the whole plant to relieve fever . In addition, the plant extract is rubbed on the skin to treat allergic reactions. In Jammu and Kashimir, India, A. roxburghiana is also used to treat skin allergies . In northern Pakistan, an extract of the whole A. roxburghiana plant is used to treat fever and malaria; a powder of the whole plant is taken for intestinal worms . Indigenous people living in the Khyber Pakhtunkhwa Province of Pakistan use the leaves of A. roxburghiana to treat chest cold, sore throat, and toothache . A. roxburghiana is used in ethnoveterinary medicine in Uttarakhand, India, to treat eye diseases, wounds, cuts, and external parasites .
As seen with other Artemisia species, there is a wide variation in the essential oil compositions of A. roxburghiana, and some of these variations can be attributed to altitude. The essential oil of A. roxburghiana from Bhaldana, Uttarakhand (850 m asl) had β-caryophyllene (18.4%) and eugenol (16.2%) as the major components, while the oil from Bhatwari, Uttarakhand (1218 m asl) had β-caryophyllene (16.3%) and α-thujone (12.0%) as major components , and the major components of the essential oil from Mussoorie, Uttarakhand (2205 m asl) were borneol (21.2%), linalyl acetate (7.4%), and α-humulene (6.7%) . Conversely, A. roxburghiana oil from Kedarnath, Uttarakhand (3200 m asl) was dominated by β-thujone (65.3%) . A. roxburghiana, plants were grown in Garniga, Trento, Italy (800 m asl), from seeds that were collected between 2600 and 4600 in the Kumbu valley of Nepal. The essential oil from these plants were rich in 1,8-cineole (16.6%), camphor (15.2%), and α-thujone (10.0%) . Apparently, there have been no reports on the biological activities of Himalayan A. roxburghiana essential oils, and it is difficult to draw any correlations between ethnobotanical use and phytochemical compositions with such wide variations in their compositions.
Artemisia scoparia (syn. A. capillaris) is widespread and common throughout southwest Asia and central Europe. The aerial parts of A. scoparia yield an essential oil with medicinal properties, and has been reported to possess insecticidal, antioxidant, antibacterial, anticholesterolemic, antipyretic, antiseptic, cholagogue, diuretic, purgative and vasodilatatory activities . A. scoparia essential oils are generally rich in diacetylenes. Thus, the leaf oil of A. scoparia collected from Milam glacier, Uttarakhand, India, was composed of capillene (60.2%), γ-terpinene (11.1%), and 1-phenyl-2,4-pentadiyne (1.0%), while the root essential oil was dominated by capillene (82.9%) and 1-phenyl-2,4-pentadiyne (2.6%) . In contrast, the essential oil from the aerial parts of A. scoparia cultivated in New Delhi was composed largely of myrcene (24.4%), γ-terpinene (18.3%), p-cymene (17.4%), and neral (12.5%) , while A. scoparia essential oil from Tajikistan was made up of β-pinene (21.3%), 1-phenyl-2,4-pentadiyne (34.2%), myrcene (5.2%), and capillene (4.9%) . A capillene-rich (42.1%) essential oil of A. scoparia from Uttarakhand showed excellent antibacterial activity against S. aureus and B. subtilis with MIC values of 12.5 μg/mL .
Inhabitants of the Nanda Devi National Park, Uttarakhand, India, apply a paste of the leaves of A. scoparia on cuts and wounds . The leaf powder is taken to treat diabetes and as a blood purifier, to treat abdominal complaints, colic, cough, and cold. People in the Agra Valley, Parachinar, Pakistan, use the whole plant of A. scoparia to treat burns, jaundice, and ear ache; the volatiles of the plant are inhaled for chest congestion . The biological activities of A. scoparia and its essential oils are likely due to capillene. This compound has shown antibacterial and antifungal activities [326,327].
Artemisia vulgaris is used in Nepal to treat various ailments . The crushed leaves are inserted into the nose to stop bleeding. A bath prepared with the crushed leaves is used to treat allergic reactions. Raw leaves are chewed as a treatment for oral ulcers. In northern Pakistan, the leaf extract of A. vulgaris is used to treat malaria and fevers . In Sudhan Gali, Kashmir, Pakistan, an extract of the leaves is used for the treatment of ophthalmic diseases . The leaf essential oil of A. vulgaris, collected from Hetauda Makwanpur, Nepal, was found to contain α-thujone (30.5%), 1,8-cineole (12.4%), and camphor (10.3%) . This essential oil was screened for antimicrogial activity against B. cereus, S. aureus, E. coli, P. aeruginosa, and A. niger, but was found to be inactive (MIC = 2500 μg/mL). Another A. vulgaris essential oil sample from Nepal did exhibit antibacterial activity against Streptococcus pyogenes and Propionibacterium acnes .
Cinnamomum represents a genus of evergreen aromatic trees belonging to the Lauracaeae comprised of approximately 250 species , out of them only eight species have been found in the Nepalese Himalayan region: C. bejolghota (Buch.-Ham.) Sweet, C. camphora (L.) J. Presl, C. glanduliferum (Wall.) Meisn., C. glaucescens (Nees) Hand.-Mazz., C. impressinervium Meisn., C. parthenoxylon (Jack) Meisn., C. tamala (Buch.-Ham.) Nees and Eberm., and C. zeylanicum Breyn. . This is a very important genus from the aspect of commercial essential oil production.
Traditionally in Nepal, C. camphora has been used to treat bronchitis, cold, congestion, diarrhea, dysentery, edema, influenza, flatulence, metabolic and heart problems, as well as various gynecological problems . Five different essential oil chemotypes of C. camphora have been identified: (1) camphor, (2) linalool, (3) 1,8-cineole, (4) nerolidol, and (5) borneol . The leaf essential oils of C. camphora from Hetauda, central region, Nepal , Pantnagar, Uttarakhand, India , and Naukuchiatal, Uttarakhand, India  were all found to be the camphor chemotype. C. camphora leaf oils have shown antifungal activity against Choanephora cucurbitarum  and antibacterial activity against Pasturella multocida  and Aspergillus niger . In addition to antimicrobial activities, the leaf oil sample from Nepal had shown notable allelopathic activity, cytotoxic activity against MCF-7 human breast tumor cells, and insecticidal activity (Chaoborus plumicornis, Pieris rapae, Drosophila melanogaster, Solenopsis invicta × richteri) . The traditional use of C. camphora to treat bronchitis, colds, and chest congestion is supported by laboratory and clinical investigations. In a Guinea-pig model, camphor vapor was shown to significantly reduce (33%) coughing . A clinical study of topical “vapor rub” containing camphor, menthol, and 1,8-cineole, showed it to be superior to a petrolatum control . In addition, camphor has shown antibacterial activity against the respiratory pathogen Haemophilus influenza .
People living in the Dolakha district of Nepal apply a paste from the roots of C. glanduliferum to treat wounds and toothache . In northern India, leaves of C. glanduliferum are used as a stimulant, carminative, and to treat coughs and colds . A leaf oil sample from northern India, rich in 1,8-cineole (41.4%), α-pinene (20.3%), and α-terpineol (9.4%), was found to have antibacterial activity against Gram-positive bacteria (Micrococcus luteus) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Aeromonas salmonicida). The high concentration of 1,8-cineole likely contributes to its efficacy against coughs and colds. 1,8-Cineole has shown clinical efficacy as a mucolytic and spasmolytic as well as beneficial effects in inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD) [336,337]. The antibacterial activity of C. glanduliferum leaf oil is likely not due to 1,8-cineole alone , but may be attributed to synergistic effects between 1,8-cineole and other minor components [339,340]. Another chemotype of C. glanduliferum, rich in (E)-nerolidol (52.2%), has been reported, but no biological activities were investigated for this oil . (E)-Nerolidol has shown antibacterial activity, however [341,342].
C. glaucescens, commonly known as “sugandhwal kokila”, has been traditionally used as demulcent and stimulant and has shown analgesic, antiseptic, astringent, and carminative properties . Seeds of C. glaucescens are used for treatment of common cold, cough, toothache and taenias; the seed paste is applied to treat muscular swellings; the seed oil has also been demonstrated to treat muscular spasm, joint pain and body aches. . In Manipur, India, the powdered bark is used to treat kidney trouble . The fruit essential oil of C. glaucescens from Nepal was dominated by methyl (E)-cinnamate (40.5%) , whereas a commercial fruit essential from Nepal had methyl (E)-cinnamate (14%) 1,8-cineole (13%), and α-terpineol (7%) as the major components, while the pericarp oil was rich in 1,8-cineole (56%) . The essential oil obtained from fruits from Lucknow, India, was also rich in 1,8-cineole (43.6%) . In comparison, the leaf oil of C. glaucescens from northeast India contained elemicin (92.9%) and methyl eugenol (4.9%) as major components . The fruit essential oil from Nepal showed nematicidal (Caenorhabditis elegans) and insecticidal (Culex pipiens, Reticulitermes virginicus) activity , while the fruit oil from Lucknow was insecticidal (Callosobruchus chinensis) and antifungal (Aspergillus flavus) . The nematicidal activity of C. glaucescens fruit oil is consistent with the traditional use of the plant to expel tapeworms. Methyl (E)-cinnamate was shown to be active against C. elegans, but 1,8-cineole was not .
Cinnamomum tamala leaf essential oil has shown some variation in composition. Cinnamaldehyde is generally a major component [97,101,108], but a leaf oil sample from Pannagar, Uttarakhand was dominated by eugenol (65%) . By contrast, C. tamala leaf oil from Karachi, Pakistan, was composed largely of β-caryophyllene (25.3%), linalool (13.4%), and caryophyllene oxide (10.3%) . In far-western Nepal, leaves of C. tamala are used to treat gastic problems , while in the Kathmandu area of Nepal, the leaves are used as a spice and flavoring agent . The leaf oil from Uttarakhand has shown activity against foodborne bacteria, Salmonella enterica, Escherichia coli, and Pasturella multocida . A leaf oil sample from Jharkhand, India, demonstrated antifungal activity against Aspergillus niger, Aspergillus fumigatus, Candida albicans, Rhizopus stolonifer, and Penicillium spp., but the composition of the oil was not reported .
Aromatic grasses are one of the chief sources of essential oils. The genus Cymbopogon is comprised of about 140 species worldwide, out of which 45 species have been reported to occur in India. Cymbopogon is one of the most important essential oil yielding genera of the family Poaceae [347,348,349]. The most common economic species viz., C. winterianus Jowitt ex Bor, C. flexuosus (Nees ex Steud.) Will. Watson, C. martinii var. motia Bruno, C. martinii var. sofia Bruno, C. nardus var. nardus (L.) Rendle, C. citratus (DC.) Stapf, C. pendulus (Nees ex Steud.) Will. Watson, C. jwarancusa (Jones) Schultz, and C. khasianus (Munro ex Hack.) Stapf ex Bor, produce different types of essential oils, such as palmarosa oil (C. martinii var. motia), lemongrass oil (C. citratus, C. flexuosus), citronella oil (C. winterianus, C. nardus), ginger grass oil (C. martinii var. sofia), or rusa oil (C. martinii var. motia) of commercial interest [350,351,352]. Three Cymbopogon grasses, namely, Java citronella (C. winterianus), East Indian lemongrass (C. flexuosus and C. pendulus) and palmarosa (C. martinii var. motia) are the most common species that are widely cultivated for their essential oils of commercial importance used in perfumes, soaps, cosmetics, toiletry, tobacco products and other related industrial products [353,354]. In India, the total area under cultivation of these aromatic grasses is more than 40 thousand hectares, distributed mainly in Assam, Kerala, Madhya Pradesh, South Gujarat, Karnataka, Maharashtra, Andhra Pradesh and Uttar Pradesh [355,356,357,358]. Several Cymbopogon species have demonstrated considerable anthelmintic, anti-inflammatory, analgesic, anti-ageing, pesticidal, antimicrobial, mosquito repellant, and larvicidal activities and thus, are used in native medicine for curing a number of diseases [350,359,360]. The Cymbopogon species have great prospects for producing quality essential oils [359,360], and it has direct relevance to the perfumery industry with economic benefit to humankind [361,362].
Lemongrass oil is distilled from two morphologically different species of lemongrass, C. flexuosus (common name: East Indian lemongrass) and C. citratus (common name: West Indian lemongrass). Geraniol (30.5%), citronellol (24.1%), neral (10.3%), and geranial (13.6%) have been reported as the major components of C. flexuosus , but many chemotypes / cultivars / variants have been reported for C. flexuosus [364,365,366,367,368,369,370,371,372,373]. The oil of lemongrass is widely used in soaps and detergents . The antifungal, antibacterial, and antioxidant properties of lemongrass oil have been widely utilized [59,374,375,376,377,378,379,380,381].
The North Indian lemongrass oil (C. pendulus) occurs in wild areas of northern India such as Saharanpur (in the state of Uttar Pradesh)  and western Nepal , and is generally rich in geranial (48%) and neral (33%), with lesser amounts of geraniol (5%) and linalool (3%) . Palmarosa oil, distilled from C. martinii var. motia, has geraniol as the major component (71%–89%)  and is considered better in quality [385,386]. The essential oil produced from the sofia variety of C. martinii Stapf is known as gingergrass oil. The cis and trans forms of p-menth-2,8 diene-1-ol, p-menth1(7),8 dien-2-ol, carveol, and piperitol, along with limonene (20%) and monoterpene alcohols, have been reported from the wild strain of C. martinii var. sofia growing in Kumaon hills [355,385]. A new hemiacetal bis monoterpenoid compound cymbodi acetal was characterized in the oil of C. martinii .
The leaf essential oil from C. jwarancusa (Jones) Schult. is rich in piperitone, imparting a characteristic odor . The major components in C. jwarancusa oil are piperitone (45%–67%) and elemol (7%–29%) [389,390,391,392].
The components of the essential oils of C. distans differ with growth conditions and geographical locations . Thus, for example, the essential oil from Munsyari (Uttarakhand) was composed of citral (neral + geranial) (35.0%), geranyl acetate (15.0%), and geraniol (9.5%) . Similarly, the essential oil cultivated in Pantnagar, Uttarakhand was made up predominantly of geranial (22.8%), neral (16.9%), geraniol (14.8%), and geranyl acetate (19.5%) . However, the oil from Nainital (Uttarakhand) was dominated by α-oxobisabolene (68%) , while C. distans var. Loharkhet essential oil was rich in the sesquiterpenoids eudesmanediol (34.4%) and 5-epi-7-epi-α-eudesmol (11.2%) . Mathela and co-workers had recognized four chemotypes of C. distans from the Kumaon and Garhwal regions of Uttar Pradesh (India) having marker compounds α-oxobisabolene (chemotype I); citral, geraniol, and geranyl acetate (chemotype II); piperitone, limonene, and eudesmanediol (chemotype III); and sesquiterpene alcohols (chemotype IV) in their oils . A study carried out by Lohani and co-workers  revealed three additional distinct chemotypes: Chemotype I (p-menth-2-en-1-ol, piperitol, α-terpinene), chemotype II (borneol, bornyl acetate, limonene), and chemotype III (piperitone, α-terpinene), to give a total of seven different chemotypes for C. distans.
There are around 75 species of Juniperus (Cupressaceae), and is a very diverse genus ranging in habitat from sea level to above timberline . Important medicinal species include J. communis, the common juniper used to flavor gin , J. drupacea from the eastern Mediterranean , J. monosperma from southwestern North America , J. oxycedrus, the heartwood from which oil of cade is prepared , and J. virginiana, used in traditional medicine by Native Americans in eastern North America .
In the Himalaya of Nepal and northern India, there are at least six species of native Juniperus: J. communis L., J. indica Bertol., J. macropoda Boiss (syn. J. excelsa M. Bieb.), J. pseudosabina Fisch. and C.A. Mey., J. recurva Buch.-Ham. Ex D. Don (syn. J. squamata Lamb.), and J. wallichiana Hook. f. and Thomson ex E. Brandis [397,403,404,405,406]. J. communis is the most widespread species of Juniperus and is distributed circumpolar, including the Himalayas from Kashmir to Bhutan . J. communis is used in traditional medicine throughout the Himalayas. For example, the local people in Kishtwar, Jammu and Kashmir, India, apply the oil extracted from the plant to treat rheumatism . Similarly, inhabitants of Parvati valley in Himachal Pradesh use an extract from the twigs to treat joint pain . Essential oils of J. communis are rich in α-pinene and limonene , and both α-pinene [408,409] and limonene  have shown antinociceptive effects in rodents, consistent with the ethnobotanical use of J. communis to treat joint pain. In addition to using the plant for gout, chronic arthritis, and rheumatism, J. communis is taken as a tonic, diuretic, for urinary tract infection , and a paste made from the leaves is applied to skin ailments . Essential oils from the berries of J. communis have shown antifungal (Candida albicans, Candida kefyr, Epidermophyton floccosum, Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis) and antibacterial (Bacillus cereus) activity [146,147,148], which is consistent with its use to treat urinary tract infection and skin infections.
In the Humla district of western Nepal, a decoction of the leaves and berries of Juniperus indica are consumed to treat coughs and colds; a paste of the berries is applied externally to cure skin diseases . Similarly, inhabitants in Upper Mustang, Nepal, use the fruits and leaves of J. indica for skin diseases, fevers, and coughs . The leaf and berry essential oils of Juniperus indica are generally rich in sabinene and terpinene-4-ol [149,151,152]. Terpinen-4-ol has shown antibacterial activity against several bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) , respiratory tract pathogens Haemophilus influenza, and penicillin-resistant Streptococcus pneumoniae . In addition, terpinen-4-ol been shown to inhibit the growth of human melanoma (M14 WT) cells . Terpinen-4-ol has shown antifungal activity against several dermatologically important fungi, including Candida albicans (responsible for cutaneous moniliasis), Candida parapsilosis (responsible for onychomycosis), and several dermatophytes responsible for tinea in humans (Trichosporon spp., Rhodotorula rubra, Epidermophyton floccosum, Microsporum canis, and Trichophyton mentagrophytes); the compound was also active against the potential pulmonary fungal pathogens Aspergillus niger, Aspergillus flavus, and Aspergillus fumigatus . Thus, the biological activities of terpinene-4-ol in J. indica oils are consistent with the ethnobotanical uses of the plant for respiratory and dermal infections.
In Himachal Pradesh, the berries of Juniperus macropoda are used to treat colic, cough, chest colds, diarrhea, impotency, and indigestion; the resin is used externally on ulcers . In the Ladakh range in northern Jammu and Kashmir [153,416] and in Tibet , the needles are used as incense. In Tibet, the needles are used medically to treat kidney diseases , while in Ladakh, tablets prepared from the wood is used for irregular menstrual cycles, amenorrhea or dysmenorrhea  and tablets made from J. macropoda berries, mixed with several other plants, are taken for kidney and urinary disorders . The leaf essential oils of J. macropoda have shown wide variation in chemical composition. A sample of leaf oil from Chamba, Himachal Pradesh had sabinene (27.5%), cedrol (14.1%), and terpinen-4-ol (9.4%) as the major components . This oil did show antifungal activity and mosquito larvicidal activity. A leaf oil sample from Hindokhal, Uttarakhand, was dominated by β-elemene (42.5%) trans-sabinene hydrate (8.8%), and α-cubebene (7.9%) , while another sample, from Mussorie, Uttarakhand, was rich in α-thujone (22.6%), biformene (7.7%), sabinene (5.8%) . Unfortunately, there do not seem to have been any phytochemical investigations on J. macropoda from Kashmir.
There do not seem to be any published reports on ethnopharmacological uses of Juniperus pseudosabina. J. recurva, on the other hand, is used in Nepal. Thus, the local people in the Rasuwa district of central Nepal use J. recurva to treat fever, headache, coughs, and colds ; the local people in the Humla district of northwestern Nepal, apply a paste of the leaves and berries to treat skin conditions . In the Nubra River valley of northern Jammu and Kashmir, the people use a decoction of the leaves of J. recurva to lower fever in children . Leaf essential oils of J. recurva are rich in δ-3-carene , but there have apparently been no bioactivity studies on J. recurva essential oils.
Nepeta (Lamiaceae) is a genus of about 250 species of flowering herbs, small shrubs, rarely trees, often with quadrangular stems, glandular and aromatic, with opposite leaves placed successively at right angles to each other . Among 31 species reported in the Himalayan region, six are found in the Kumaun region of Uttarakhand: N. ciliaris Benth., N. connata Royle ex Benth., N. distans Royle ex Benth., N. elliptica Royle ex Benth., N. leucophylla Benth., and N. spicata Wall ex Benth. . Eleven species of Nepeta are native to Nepal: N. cataria L., N. ciliaris, N. coerulescens Maxim., N. discolor Royle ex Benth., N. elliptica, N. hindostana (Roth) Haines, N. laevigata (D. Don) Hand.-Mazz., N. lamiopsis Benth. ex Hook. f., N. leucophylla, N. nepalensis Spreng., and N. staintonii Hedge . In addition, N. campestris Benth. and N. eriostachys Benth. are endemic to Kashmir, India .
Nepeta species are used traditionally as antispasmodic, diuretic, febrifuge, diaphoretic, antimicrobial and antiseptic agents and also in the treatment of dysentery, tooth trouble and kidney and liver diseases . Diverse biological activities, e.g., feline attractant , insect repellant , and arthropod defense [426,427] are attributed to the presence of biologically active iridoids, monoterpene nepetalactones, in Nepeta species . Aydin et al. investigated the antinociceptive effects of essential oils from Nepeta species, including N. phyllochlamys, N. nuda ssp. nuda, and N. caesarea, using a tail flick and tail immersion tests . These authors detected central and peripheral antinociceptive effects in N. caesarea and concluded that 4aα,7α,7aα-nepetalactone was the active principle and had a specific opioid receptor subtype agonistic activity.
Nepeta species are used in the traditional medicine of many cultural groups in the Himalayas. Many species are used to reduce fever, treat coughs and colds, and relieve digestive disorders (Table 1). Nepetalactones are generally considered biochemical markers for the genus and some some Himalayan Nepeta essential oils are rich in nepetalactones, e.g., N. elliptica  and N. juncea . The antimicrobial activities of these essential oils are likely due to nepetalactone concentrations [430,431,432]. Nevertheless, many Himalayan Nepeta samples contain little or no nepetalactones , and therefore, the ethnomedicinal uses and biological activities observed in these Nepeta species are likely due to other constituents.
Some Nepeta spp. have large concentrations of 1,8-cineole, viz. N. discolor , N. laevigata , and N. royleana . Although 1,8-cineole has been shown not to have antitussive activity [333,433], the compound has shown efficacy in acute rhinosinusitis and alleviate headache, nasal obstruction, and rhinological secretion in a double-blind, placebo-controlled study . In addition, 1,8-cineole has demonstrated ulcer-healing and gastroprotective properties in rats  as well as antispasmodic effects on isolated mouse ileum . Several other Nepeta samples have been rich in sesquiterpenoids such as β-caryophyllene [200,204,209,214,218], caryophyllene oxide [201,214,218], and germacrene D [200,204,209,218] (see Table 1). β-Caryophyllene has shown anesthetic , anti-inflammatory activity , but not analgesic activity , in animal models. The compound ameliorated colitis in a mouse model [440,441] and has shown antispasmodic effects on isolated rat ileum . Caryophyllene oxide has shown analgesic as well as anti-inflammatory activity in mice .
The members of the genus Origanum L. are usually perennial herbs belonging to the mint family (Lamiaceae). It has been classified into 10 sections including 43 species, 6 subspecies, 3 varieties and 18 naturally occurring hybrids, widely distributed in the Mediterranean, Euro-Siberian and Irano-Siberian regions [444,445]. Members of the genus are mainly distributed along the Mediterranean region, with 75% restricted to the eastern Mediterranean . The genus includes some commercially important culinary herbs, including oregano (Origanum vulgare L.) and marjoram (Origanum majorana L., syn. Majorana hortensis Moench), which are extensively used for flavoring food products and alcoholic beverages. In India and Nepal, only one species is available from sub-tropical to alpine zones of the Himalayan Region .
Origanum vulgare commonly is known as “oregano” in most European countries and “Himalayan marjoram” or “Indian oregano” in India. This is the only species reported from northwestern Himalaya, found in an altitude between 600 and 4000 m of Kumaon and Garhwal region of Uttarakhand Himalaya . There are numerous chemotypes of O. vulgare, and Verma and co-workers have defined six in Himalayan India : (1) γ-terpinene/thymol, (2) thymol/ocimene, (3) thymol/γ-terpinene, (4) γ-terpinene/carvacrol, (5) carvacrol/γ-terpinene, and (6) linalool. Lukas and co-workers have generalized European O. vulgare monoterpene chemotypes as (a) cymyl-type (rich in p-cymene, thymol, and/or carvacrol), (b) acyclic-type (rich in myrcene, ocimene, linalool and linalyl derivatives), and (c) sabinyl-type .
The thymol- and carvacrol-rich chemotypes of O. vulgare should be useful in treating bronchial and pulmonary diseases (coughs, colds, etc.); both thymol and carvacrol are antibacterial , antitussive [449,450], antihistamine , and numerous other pharmacological properties , which are consistent with traditional uses of this plant. The monoterpenoid alcohols, linalool, terpinen-4-ol, and α-terpineol [338,453], the sesquiterpenoids β-caryophyllene, α-humulene, and germacrene D  have also shown antimicrobial effects, consistent with the potential activities and uses of the other chemotypes of O. vulgare.
Valeriana L. (Caprifoliaceae) consists of around 200 species distributed in the temperate and sub-tropical areas globally and is among the important herbal traditional drug in various pharmacopeias . The herbal drug valerian consists of the subterranean organs (rhizome, root, stolons) of Valeriana officinalis L. . The valerian-derived phytomedicines have been used for curing nervous unrest, emotional troubles (as tranquillizer/sedative), epilepsy, insanity, snake envenomation, eye-trouble, skin-diseases, relaxant, carminative, and for improving the complexion [455,456,457]. Valerian is one of the top ten selling herbal supplements in North America . It has also been prescribed as the perfect herbal tranquilizer, and was used for this purpose in the First World War to treat soldiers suffering from shell shock and to calm civilians subjected to air raids during World War II .
In India, Valeriana jatamansi Jones (syn. Valeriana wallichii DC.). has long been used in Ayurveda and Unani systems of medicine, which describe its use in skin diseases, insanity, epilepsy, and snake bite, and is considered to have remarkable sedative effects in nervous unrest, stress, and neuralgia [460,461]. A survey of the literature has revealed the presence of flavonoid glycosides [462,463], iridoids, and lignans [464,465,466] in V. jatamansi. Anti-inflammatory  antianxiety , antidiarrheal, and bronchodilatory activities  of V. jatamansi extracts have been scientifically validated. The plant has also shown in vitro cytotoxic  and antileishmanial  activities. V. jatamansi essential oil has shown antimicrobial activity against pathogenic bacteria and as well as antifungal activity against different human and plant fungal pathogens .
The chemical compositions of root/rhizome essential oils show six chemically distinct chemotypes within V. jatamansi. (a) a maaliol-rich (~ 40%–60%) chemotype [287,288], (b) a patchouli alcohol-rich (> 40%) chemotype [288,289,290,291], (c) a patchouli alcohol/α-bulnesene chemotype [289,291], (d) a patchouli alcohol/viridiflorol chemotype , (e) a seychellene-rich chemotype , and (f) a kanokonyl acetate chemotype . The root oil of V. himalayana from Talle valley of Arunachal Pradesh was mainly composed of methyl linoleate, valeracetate, bornyl acetate, and cuparene . The roots of V. hardwickii var. arnotiana revealed constituents belonging to two different chemotypes : Chemotype I, collected from an altitude of 3500 m from Milam glacier contained valeracetate, 8-epikessyl glycol diacetete, α-kessyl acetate, and malliol as the marker compounds, while chemotype II, collected from Vishnu Prayag, contained kessanyl acetate and maaliol as the main constituents. Epoxysesquithujene, a novel sesquiterpenoid, was isolated from V. hardwickii var. hardwickii . The main constituents of root oil of V. pyrolaefolia were valeranone and patchouli alcohol .
The Himalayas, with wide-ranging elevations, deep glacial and river valleys, areas of high rainfall and areas of high desert, is a rich area of biodiversity with much endemism. Traditional herbal medicine continues to play a role in many tribal areas, and numerous medicinal plants and their essential oils have shown remarkable biological activities. Unfortunately, there remains a paucity of information relating biological activities of essential oils with the ethnobotanical uses of the plants. In many cases this may be due to the activity residing in non-volatile components. Additionally, many phytochemical researchers have neglected bioactivity screening related to ethnopharmacological uses. Thus, there is much additional work that can be carried out to identify phytochemicals associated with biological activities that support traditional uses of medicinal plants. In addition, several aromatic plants have shown commercial promise as flavoring agents, fragrances, cosmetics, and pesticides. Due, in part, to the great demand for essential oils, herbal medicines, and pharmaceuticals, the medicinal plants of the Himalayas are threatened by unsustainable harvesting , and increasing environmental degradation, invasive plant species, and climate change also threaten Himalayan native flora. We encourage the preservation of traditional knowledge and uses of Himalayan medicinal plants and we hope that additional steps are undertaken to protect and maintain the Himalayan ecology.
R.K.J., P.S. and W.N.S. conceived and organized the review and contributed to the writing and editing of the manuscript.
The authors declare no conflict of interest.