Bioassay-Guided Isolation of Anthelmintic Components from Semen pharbitidis , and the Mechanism of Action of Pharbitin.

Parasitic helminths continue to pose problems in human and veterinary medicine, as well as in agriculture. , the seeds of (Linn.) Choisy (Convolvulaceae), is a well-known traditional Chinese medicinal botanical preparation widely used for treating intestinal parasites in China owing to its desirable efficacy. However, the anthelmintic compounds in and their mechanism of action have not been investigated yet. This study aimed to identify the compounds active against helminths from and to establish the mechanism of action of these active compounds. Bioassay-guided fractionation was used to identify the anthelmintic compounds from . The anthelmintic assay was performed by monitoring () motility with a WMicrotracker instrument. Active compounds were identified by high-resolution mass spectrometry. Several (analogues of) fragments of the anthelmintic compounds were purchased and tested to explore the structure-activity relationship, and to find more potent compounds. A panel of mutant strains resistant to major currently used anthelmintic drugs was used to explore the mechanism of action of the active compounds. The bioassay-guided isolation from an ethanol extract of led to a group of glycosides, namely pharbitin (IC: 41.0 ± 9.4 μg/mL). Hit expansion for pharbitin fragments yielded two potent analogues: 2-bromohexadecanoic acid (IC: 1.6 ± 0.7 μM) and myristoleic acid (IC: 35.2 ± 7.6 μM). One drug-resistant mutant ZZ37 demonstrated a ~17-fold increased resistance to pharbitin compared with wild-type worms. Collectively, we provide further experimental scientific evidence to support the traditional use of for the treatment of intestinal parasites. The anthelmintic activity of is due to pharbitin, whose target could be UNC-63 in .