Passionflower (also known as maypop or apricot vine) is a perennial, woody, climbing vine native to the southeastern United States. Reaching up to roughly ten meters in length, passion flower has gray, striated bark and alternate, palmate leaves with three to five finely toothed lobes. The plant flowers from early to late summer, producing rayed blossoms with a diameter of 5 to 9 centimeters. The flowers consist of five sepals, which are white on the inside and green on the outside, and five petals, which are white to pale red. At the center of the flower is a secondary corona consisting of four rings of purple, threadlike structures. The fruit (or granadilla) is a smooth, yellow-orange, ovate berry, about 7 or 8 centimeters long, with sweet, edible pulp and numerous seeds. The above-ground portions of the plant are used for health promoting purposes.
Although medical use of passionflower did not begin until the mid 19th century, the plant has a history of religious symbolism that begins more than two hundred years earlier, when Jesuit missionaries viewed the plant's attributes as representative of various elements surrounding the crucifixion (or passion) of Christ and, thus, named it passionflower. While passionflower's religious significance would fade over time, the plant would eventually become the center of political controversy. In 1919, the General Assembly of Tennessee designated that a state flower be chosen by the school children of the state, and passionflower was selected. This designation was called into question in 1933 when the state legislature selected the iris as the "State Flower of Tennessee" without formally rescinding the previous selection of passionflower. To rectify the confusing situation, in 1973 passionflower was named the state wildflower and the iris the state cultivated flower. Passionflower was introduced into medicine in 1840 by Dr. L. Phares of Mississippi, but remained largely obscure until it was reintroduced by eclectic physicians later that century. For many years following, the herb was used as a calmative herb, and it was listed in The National Formulary from 1916 to 1936. Although passionflower has since fallen out of use in the U.S., it remains popular as a medicinal herb in Germany and other European countries.
The constituents responsible for passionflower's activity in the body are still the subject of debate. It is possible that the herb's effects stem from the interaction of multiple principles. Compounds found in passionflower include coumarin derivatives, maltol, and small amounts of essential oil and alkaloids. The plant also contains numerous flavonoids, including vitexin, isoorientin, schaftoside, isoshaftoside, and chrysin, which may contribute to its biological activity.
The daily dosage approved by Commission E is 4 to 8 grams of the herb or equivalent preparations. To make an infusion, 150 milliliters of water can be poured over one teaspoon of the herb and strained after ten minutes. There are no known health hazards or side effects at this dosage range. Passionflower toxicity has been reported in the case of a 34-year-old Australian female who experienced such symptoms as nausea, vomiting, drowsiness, and accelerated heart rate; however, the amount, purity, and potency of the formulation used in this case have not been determined.