Indigenous to the tropical regions of North America, passionflower is now cultivated throughout Europe. This plant was supposedly given the name passionflower because its corona resembles the crown of thorns worn by Christ during the crucifixion.

The dried flowering and fruiting tops of passionflower are used in traditional herbal remedies for nervousness, insomnia, and convulsion. During the early twentieth century, this plant was a popular sedative and calmative, and was listed in the United States National Formulary between 1916 to 1936. In 1978, the U.S. FDA banned the use of passionflower in OTC preparations, citing the lack of valid evidence to support its safety or efficacy in the treatment of nervousness or insomnia.

A survey conducted in 1986 indicated that passionflower was utilized more frequently in Britain than any other ingredient in herbal sedatives. In Germany, Commission E has approved the use of this herb as a tranquilizer. Commission E's decision was based on evidence showing that passionflower reduced mobility in laboratory animals. A number of sedative-hypnotic pharmaceutical preparations sold in Europe, including a sedative chewing gum, contain passionflower extract.

Scientific research confirms that passionflower has an in vivo motility-inhibiting effect. However, the active principles responsible for this effect have not been unequivocally established. Passionflower contains C-glycoside flavonoid constituents and small quantities (up to 0.01%) of harmala-type indole alkaloids. The sedative effects are presumably not due to these compounds, however, since harmala-type alkaloids tend to act as stimulants rather than depressants.

Passionflower is a perennial climbing vine with herbaceous shoots and a sturdy woody stem that grows to a length of nearly 10 m. The three-lobed leaves are alternate, petiolate, and finely serrated. The flowers are characteristically yellow or flesh-colored, with tinges of purple and a sweet fragrance. Each flower has five petals varying in color from white to pale red. Inside the petals is a secondary corolla composed of four thread wreaths. These form rays that surround the axis of the flower. The ripe fruit is an orange-colored, multi-seeded, ovoid berry containing an edible, sweetish yellow pulp.

Part Used/Pharmaceutical Designation

• Flowers
• Leaves
• Stems
• Other: above-ground (aerial) parts; herb

Flavonoids (up to 2.5%): C-glycosylflavones (isovitexin-2"-glucoside, schaftoside, isoschaftoside, isoorientin, isoorientin-2"-glucoside, vicenin-2, lucenin-2), apigenin, luteolin glycosides (e.g., orientin, homoorientin, lucenin); kaempferol, quercetin, rutin. Cyanogenic glycosides: gynocardine (less than 0.1%). Indole-type alkaloids (up to 0.01%): harman, harmaline, harmalol, harmine, harmol (putative constituent). Other constituents: maltol (0.05%), ethylmaltol, passicol (a polyacetylene), fatty acids, formic acid, butyric acid, sitosterol stigmasterol, gum, volatile oil (trace). Root contains coumarins (scopoletin and umbelliferone).

Passionflower commercial preparations are made from the fresh or dried aerial parts. Both whole and cut raw plant material are used in teas and infusions. For optimal results, flowering shoots, growing 10 to 15 cm above the ground, are harvested after the first fruits have matured and then either air-dried or hay-dried. Some (but not all) experts recommend collecting the shoots two times each year to coincide with maximum quantity of flavonoids. The content of harman alkaloids also fluctuates, and plant material containing more than 0.01% harman alkaloids should be avoided.

Traditional uses: used internally as sedative, mild hypnotic, antispasmodic, and anodyne (analgesic) for nervous agitation, insomnia, hysteria, diarrhea, dysentery, neuralgia, generalized seizures, nervous tachycardia, spasmodic asthma, dysmennorhea; used externally for hemorrhoids. Also incorporated into homeopathic preparations.

Conditions: nervousness, insomnia

Clinical applications: nervous restlessness and agitation, insomnia, nervous gastrointestinal conditions

In in vitro studies, passicol, one of the main active constituents in passionflower, showed antimicrobial action against several pathogens, including bacteria such as hemolytic Streptococci and Staphylococcus aureus, yeasts such as Candida albicans, and molds.

Several experiments have clearly demonstrated that passionflower has psychotropic activity. In in vivo studies, passionflower extract and some of its constituents significantly prolonged sleeping time and decreased locomotor activity. An in vivo investigation evaluated the effects of lyophilised hydroalcoholic and aqueous extracts of passionflower as well as its active principles on behavioral parameters in mice. While the hydroalcoholic extract exhibited anxiolytic (anti-anxiety) effects, the aqueous extract showed sedative action. The aqueous extract also extended sleeping time in mice previously given a sub-hypnotic dose of pentobarbital.

Maltol is a pyrone derivative isolated from an alkaloid fraction of passionflower. Japanese researchers reported that maltol produced depression and other sedative effects in mice. In other animal studies, a high dose of maltol and ethylmaltol exhibited anticonvulsant effects while a low dose of these same compounds reduced spontaneous motor activity. Both maltol and ethylmaltol had sedative action on the CNS and both potentiated sleeping time induced by hexobarbitone. However, other investigators did not attribute these effects to either the flavonoid or alkaloids in passionflower. It is also thought that maltol and ethylmaltol may mask the CNS stimulant effects of the harman alkaloids.

Expert opinion on the chemical constituents responsible for the sedative action of passionflower is divided. Even though maltol appears to be a likely candidate, some researchers have called for further studies confirming the pharmacological effects of specific active constituents. In addition, clinical investigations on the effects of passionflower on humans are urgently needed.

• Infusion: 2 to 5 g dried herb tid
• Fluid extract (1:1 in 25% alcohol): 0.5 to 1.0 ml tid
• Tincture (1:5 in 45% alcohol): 0.5 to 2.0 ml tid

No side effects reported. The value for acute toxicity of passionflower fluid extract (I.P.) was greater than 900 mg/kg in mice. Toxic cyanogenic glycosides have been isolated from related Passiflora species, but not for Passiflora incarnata.

Although passionflower extracts and preparation are generally devoid of contraindications, only limited toxicity data are available. Excessive oral intake may induce sedative effects and potentiate existing MAOI therapy. For this reason, passionflower should not be consumed in quantities higher than recommended doses. This herb should be completely avoided during pregnancy and lactation since harman and harmaline have been shown to have in vivo uterine-stimulant action in some studies.

Oral administration of an aqueous extract of passiflora incarnata (160 mg/kg) following intraperitoneal dosing with pentobarbital (50 mg/kg) significantly prolonged the sleeping time induced by the pentobarbital in rats (Speroni and Minghetti 1988).

In 1978, the U.S. FDA banned passionflower as an ingredient in OTC sedative preparations. In Britain, passionflower is on the General Sale List (GSL), and in Germany, it is authorized by Commission E for use in remedies. The Council of Europe approves passionflower as a natural source of food flavoring (category N3) that can be added to foodstuffs. However, the Council also notes that the potential toxicity of passionflower cannot be fully assessed because current information is insufficient.

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