Tian Hu Sui

Seven oleanane saponins new to science, described from the whole plant of this species by a Japanese group. They are the structurally defining saponins of Hydrocotyle sibthorpioides and are not the ursane-type triterpenes of Centella asiatica, which is the single most important chemical point about this drug.

A second series of oleanane saponins from this species, described independently by a Taiwanese group. Those bearing four sugar units, three glucoses and one arabinose, showed moderate cytotoxicity against the KB, Daoy and WiDr human tumour cell lines, which is the only direct cytotoxicity signal reported for the drug's own saponins.

A previously known oleanane saponin co-occurring with the hydrocotylosides. It is noted here because it anchors the species chemically to the Araliaceae saponin series rather than to the Centella series.

Quercetin is one of the four compounds identified as responsible for the antioxidant activity of the whole-plant extract in the study that measured this species head to head against Centella asiatica. In that comparison the Hydrocotyle extract scavenged DPPH with an IC50 of 19.7 micrograms per millilitre and inhibited lipid peroxidation with an IC50 of 12.3 micrograms per millilitre, outperforming the Centella extract.

Two of the four phenolics driving the extract's radical scavenging, metal chelation and lipid peroxidation inhibition. They are ordinary plant phenolics rather than species markers, and do not distinguish this herb from many others.

The fourth of the identified major antioxidant phenolics of the whole-plant extract. It is a plausible contributor to the traditional heat-clearing and toxicity-resolving use, though no work links it specifically to a clinical effect in this species.

A methylated flavonol reported alongside quercetin in the whole herb. It is listed here because Chinese materia medica entries for Tian Hu Sui give flavonoids rather than saponins as the leading constituent class, which sits alongside rather than contradicts the saponin isolation work.

A lignan reported from the whole herb. The coumarin question matters more than the lignan does: coumarins were attributed to this species in the older literature and have not held up on re-examination, which is worth knowing before assuming any anticoagulant-type concern for the drug.

A common plant sterol reported from this species. It has no bearing on the drug's traditional indications and is recorded only for completeness of the constituent list.

Asiaticoside is the signature triterpene glycoside of Centella asiatica, and its reported presence here is the point at which the Hydrocotyle and Centella literatures become entangled. Two separate publications on asiaticoside and on genistein from the same author group have since been retracted, in 2024 and 2025 respectively. The compound should be treated as a contested constituent of Hydrocotyle sibthorpioides, not as an established one, and no Centella asiatica dosing or efficacy data should be transferred to this drug on the strength of it.

The text usually cited as the first record of Tian Hu Sui. Its appearance in a dietary-treatment chapter rather than in the main drug list reflects its status: a southern Chinese folk and food herb rather than a drug of the mainstream materia medica line. It has no entry in the Chinese Pharmacopoeia to this day.

Carries the standard modern entry for Tian Hu Sui as the whole herb of Hydrocotyle sibthorpioides, used fresh or dried for jaundice, hepatitis, urinary stranguria, sore throat, cough and skin conditions, and applied topically for sores. Because the drug is not in the Chinese Pharmacopoeia there is no official assay, no marker compound and no purity limit for it, so identity rests entirely on the supplier.