The drug Digitalis, an extract of Digitalis purpurea, Foxglove plant, is in use since long. Medical practitioners, namely, William Withering, 1785 [1] and Hahnemann, 1803 [2], had introduced the drug in their respective systems of medicine. Out of about thirty known organic compounds of Digitalis purpurea only 4–6 are medicinally active components comprising of Digoxin, Digitoxigenin, Digoxigenin, and Saponins. Digitalis purpurea derivatives are used in treatment of diseases like heart failure, arrhythmia, neurological diseases and also being tried as antitumor [3]. Digoxin (C₄₁H₆₄O₁₄) is 300 times more potent than the powder prepared from Digitalis purpurea. It has a molecular weight of 780.95, and the absolute bioavailability of Digoxin intravenous injection is 100%. Time of onset of the effect of Digoxin after intra-venous injection is 5–30 minutes, Patients maintained on Digoxin may also use ultradiluted preparations of the same, ultimately increasing the body burden of Digoxin. Saturated extract of an aqueous ethanol mixture is used to prepare serial dilution of the drug Digitalis purpurea and is represented by the suffix “θ”. Serial dilutions also are referred to as potencies “1c” or “1” in centesimal scale, which means that one part of the “θ” saturated extract of the drug is mixed to make 100 parts of aqueous ethanol mixture and succused. When the same process is repeated 6 times, by adding 1 part of the previous potency in 99 parts of aqueous ethanol mixture and succused, after each stage starting from the first dilution for the next 5 times, “6c” or “6” potency is obtained. Presently, it is not possible to detect the serially ultradiluted drug Digitalis purpurea in biological samples. However, attempts are on to find the “evidence base” of serially ultradiluted drugs. Methods to identify the medicinally active ingredient in ultradiluted drugs have been attempted sparingly [4]. The investigation of homeopathic drugs is extremely interesting and challenging and from that point of view shows novelty. Digitalis purpurea is readily available commercially, in serial dilutions prepared with aqueous alcohol (91.4%) as diluent. The serial dilution 12c of the drug, at a ratio 10⁻²⁴, has a 60% probability of containing one molecule of original material if one mole of the original substance was used. Digitalis-like toxicity (Digitalis intoxication) results from an overdose of the drug, consumption of Digitalis purpurea plant products, and from toad skin (another animal source: butterflies) [5]. Digitalis intoxication causes anorexia, nausea, vomiting, and diarrhea, jaundiced or yellow vision, appearance of blurred outlines, reduced heart rate, and weight loss. It is also necessary to evaluate the quality of the drug in solutions/dilutions. This motivated us and necessitated detection of Digitalis purpurea in serial dilutions. Attempts had been made to detect Digoxin in solutions by various methods [6].

The drug Digitalis purpurea used in this work in potencies/ultradilutions θ, 6, 30, and 200 were procured from M/s Hahnemann Publishing Company Pvt Ltd, Kolkata, India. It was prepared with contaminant free, for example, acetone-free aqueous alcohol (91.4% ethanol and glass double distilled water mixture). The drugs were manufactured as per Indian Homeopathic Pharmacopoeia. The commercially available Digoxin with concentration 0.25mg/mL (Samarth Pharma) was procured from the local medicine vendor for the present studies. Rectified spirit/ethanol manufactured by Bengal Chemicals & Pharmaceuticals, India, was used.

The fluorescence is likely to be due to α, β-unsaturated lactone present in the compound. The fluorescence spectrum of the compound is taken at different dilutions in aqueous ethanol. In all the emission studies, the samples were excited at 255nm. The emission spectra of different dilutions are shown as C, D, and E, and purest medicinally active ingredient Digoxin is shown as B in Figure 2. These fluorescence spectra revealed that Digoxin component shows a structureless fluorescent with emission maxima at 318nm with a relative intensity of 4.5 × 10⁶. The emission spectra of Digitalis purpurea 6 are shown in Figure 2 as C6. In this case the structureless emission is found to be modified with a semistructured emission with maxima at 357nm and 374nm and further a shoulder at about 318nm remained, which could be due to the original B (Digoxin). The appearance of additional bands at 357 and 374nm may be ascribed to loss of self-quenching or dissociation of component substance due to serial dilution, and these bands showed an increase in intensity with subsequent dilutions up to a certain level [8].