Psychotria serpens

Two new iridoid glucosides from the leaves, isolated with six known congeners. All eight inhibited nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 macrophages with IC50 values between 27.2 and 61.4 micromolar, which is modest potency and consistent with a whole-fraction anti-inflammatory effect rather than a single lead. Iridoids are the class expected of a Rubiaceae and are the most useful chemical marker for distinguishing this drug from Trachelospermum jasminoides, the Apocynaceae vine it substitutes for.

An unusually heavily O-methylated flavonoid profile for a Rubiaceae, and the reason a 90 percent ethanol extract of this drug is chemically quite unlike a water decoction of it. The 2018 isolation reported these as the bulk of the extract but did not test them for activity, so their contribution to the traditional wind-damp indication is unestablished.

Three ursane triterpene acids recovered alongside the flavonoids, all first reports for the genus Psychotria. Triterpene acids of this type are the usual chemical explanation offered for the antimicrobial and anti-inflammatory behaviour of crude extracts, but they were not assayed in the paper that reported them from this plant.

A new class of glycosylsphingolipids named for the plant. They were reported from the fractions that showed activity against H460, HepG2, HeLa and gefitinib-resistant PC9 cell lines without toxicity to normal 16HBE bronchial cells, but the cytotoxicity was measured on the ethyl acetate and n-butanol fractions rather than on the isolated compounds, so the attribution is not established.

Recorded as a negative because the genus reputation invites the wrong assumption. Psychotria is best known pharmacologically for indole alkaloids, including the N,N-dimethyltryptamine of Psychotria viridis, and Rubiaceae is one of the two families in which cyclotides occur. Neither class has been reported from Psychotria serpens in any of the phytochemical surveys of it, and the flavonoid-triterpene-iridoid profile that has been found is not alkaloidal. That said, no targeted alkaloid or cyclotide screen of this species has been published, and absence of an assay is not evidence of absence.

The source usually cited for the drug's indications: dispels wind and eliminates dampness, relaxes the sinews and frees the collaterals, for rheumatic joint pain, head wind pain, numbness of the limbs, sciatica, lumbar strain, bone tuberculosis, wheezing, multiple abscesses and snakebite. This is a twentieth-century provincial survey. Psychotria serpens has no entry in the classical Chinese materia medica, and any classical pedigree claimed for it belongs to Luo Shi Teng, a different plant.

The drug's formal standing. The leafy vine stems of Psychotria serpens are a standard drug in Guangdong under a name built from that of a different Pharmacopoeia drug. The properties given are bitter and acrid, neutral, with actions of dispelling wind and stopping pain, reducing swelling, and relaxing the sinews and freeing the collaterals. Recognising that this is a provincial standard and not the Chinese Pharmacopoeia is what keeps the two Luo Shi Teng apart in practice.

The whole plant is gathered year-round as Chuan Gen Teng for weakness, rheumatic joint pain, head wind pain, childhood food accumulation, numbness of hands and feet, lumbar and leg pain, deep-seated abscess, traumatic injury, fracture and snakebite. The recorded cautions are that those with Spleen and Stomach vacuity cold should take it with care and that it is contraindicated in pregnancy and during menstruation. The Vietnamese use for rheumatism and sciatica is recorded independently in the phytochemical literature, so the wind-damp indication is attested across the plant's whole range.