Correct Identification of Passiflora incarnata Linn., a Promising Herbal Anxiolytic and Sedative

Passiflora incarnata Linn. and Passiflora edulis Sims are the two important plants of the family Passifloraceae that have often been reported as synonymous because of their identical morphological and microscopic characteristics. P. incarnata is a popular sedative and anxiolytic, whereas, P. edulis is rarely reported to possess significant central nervous system depressant activity. P. edulis, as the name of the species reflects, is mainly grown for edible purposes. During a survey of literature on the genus Passiflora, it was noticed that in many references the two plants are mentioned synonymously. The designation by Sir William J. Hooker in 1843, followed by the citation of P. edulis as the synonym of P. incarnata in Index Kewensis of 1895, not only substantiated the controversial identity but also caused confusion to researchers. The prevailing confusion might have led to improper selection of the bioactive plant, thereby accounting for inconclusive and contradictory pharmacological reports on either of the two plants. In this work, we establish key identification parameters to differentiate P. incarnata from P. edulis. Various leaf constants such as vein-islet number, vein-termination number, stomatal number, and stomatal index are different for the two species. Physicochemical parameters such as ash values and extractive values and the thin layer chromatography profile of the petroleum ether extract of P. incarnata and P. edulis are also distinct and different. Various clinical uses of P. incarnata for anxiety and allied diseases are discussed.