Comparative anxiolytic activity profile of various preparations of Passiflora incarnata linneaus: a comment on medicinal plants' standardization.

OBJECTIVES: Mother tincture preparation of Passiflora incarnata from five reputable manufacturers of homeopathic medicines were compared to the bioactive fraction of methanol extract of P. incarnata (standard) for their anxiolytic activity in mice using the elevated plus-maze model of anxiety.
MATERIALS AND METHODS: The extracts of P. incarnata were further subdivided in four doses, i.e., 100, 200, 300, and 400 mg/kg, suspended in a vehicle, and administered orally to groups of mice. Methanol extract of P. incarnata (125 mg/kg, orally) was taken as a standard. Anxiolytic activity was measured using the elevated plus-maze model. All treatments were given orally. Forty-five (45) minutes after the treatments, mice were placed on the center of the elevated plus-maze and the number of entries in open arms were measured for 5 minutes.
SUBJECTS: Studies were performed with Swiss albino mice.
RESULTS: The dried mother tincture preparations exhibited maximum anxiolytic activity at 300 mg/kg (SBL); 400 mg/kg (DWSI and DWSG); 200 mg/kg (DRCG), and nil (BHL) respectively, with reference to anxiolytic activity exhibited by the methanol extract of aerial parts of P. incarnata (125 mg/kg).
CONCLUSIONS: To ensure uniformity and consistency of the biologic effects exhibited by plant-derived phytopharmaceuticals, uniform standards are required globally. The monographs on P. incarnata mention standardization of the plant using any known flavonoid as the chemical marker and the marker compound was not the one responsible for the plants multifarious biologic effects. The recent report of a trisubstituted benzoflavone compound (BZF) as the main bioactive phytoconstituent of P. incarnata made it feasible to resort to biologic standardization of this plant using BZF as the biomarker compound. The biologic standardization would ensure bioequivalence of the medicinal preparations of P. incarnata. These studies also recommend the incorporation of leaf constants, ash values, extractive values, thin layer chromatography profile (vital "fingerprints" specific for a plant), and the quantitative assay by determining the bioactive BZF moiety in pharmacopoeias in order to ensure uniform biologic results and standards of P. incarnata because the plant currently has tremendous usefulness. The herbal pharmacopoeias, which are still in their "infancy," can be strengthened by incorporating the appropriate bioactive constituents that need to be identified by using modern technological procedures. Once the appropriate bioactive constituent(s) are established and authenticated, their qualitative and quantitative assay procedures can be developed. Reporting the vital fingerprint parameters of the plant and incorporation of assay procedures of the bioactive phytomoiety in the official monographs of medicinal plants, will certainly strengthen the herbal pharmacopoeias. This is perhaps the most important scientific approach that would ensure uniform standards and bioequivalence of plant-medicines - a need to revive faith in the healing potentials of plant-derived medicines.