Abstract
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Helicteres hirsuta Lour. (H. hirsuta) has been traditionally used as a folk medicine for treating a range of common diseases. It has been used in furuncle treatment, pain relief, dysentery, measles, flu, antimalaria and antiobesity treatments in some Asian countries, revealing that this plant material contains important bioactive compounds which are linked with health benefits and/or can act as therapeutic agents. Hence, many attempts have been made to isolate and identify the key bioactive compounds present in H. hirsuta and conduct in vitro tests to investigate their biological activities. We recently revealed that H. hirsuta leaf has a high total phenolic content (TPC: 192.6 mg gallic acid equivalents (GAE)/g) and total flavonoid content (TFC: 215.2 mg catechin equivalents (CE)/g). The stem of H. hirsuta also had high contents of TPC and TFC (212.6 mg GAE/g and 280.1 mg CE/g, respectively). The results also revealed that phenolic compounds from this plant had a strong positive correlation with antioxidant capacity including DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power (R2 range of 0.78 and 0.99), which are known to link with diverse bioactivities including antioxidant, antimicrobial, anticancer, antiobesity and antidiabetic effects. Additionally, H. hirsuta leaf and stem were found to contain high levels of saponins (808.0 and 347.5 mg escin equivalents/g, respectively), that were determined using colorimetric assay. Several individual compounds have been identified in the extracts of H. hirsuta, including rutin, methyl caffeate, 5,8-dihydroxy-7,4′-dimethoxyflavone, isoscutellarein 4′-methyl ether 8-O-β-d-glucopyranoside, 4,4′-sulfinylbis(2(tert-butyl)-5-methylphenol), 7-O-methylisoscutellarein, 7,4′-di-O-methylisoscutellarein, six lignans (pinoresinol, medioresinol, syringaresinol, boehmenan, boehmenan H and trans-dihydrodiconiferyl alcohol), betulinic acid, 3-O-trans-caffeoylbetulinic acid, 3β-benzoylbetulinic acid, betulinic acid methyl ester, lupeol, 3β-O-acetylbetulinic acid, simiarenol, stigmasterol and β-sitosterol. The derived extracts and isolated compounds from this plant have been shown to inhibit the growth of various cancer cell lines in vitro and offer a promising source of active compounds against other health problems including obesity, diabetes and malaria. Further studies on the mechanisms of bioactive compounds from this plant are suggested to elucidate their mechanisms of action for health benefits. In addition, more in vivo tests associated with clinical trials are also needed to validate and confirm their effects for further development of nutraceutical and pharmaceutical products from this plant material.
