Antituberculosis Agents and an Inhibitor of the para ‐Aminobenzoic Acid Biosynthetic Pathway from Hydnocarpus anthelminthica Seeds

Investigation on the extracts of Hydnocarpus anthelminthica seeds led to the isolation of three new compounds, anthelminthicins A–C ( 1 – 3 , resp.), and two known ones, namely chaulmoogric acid ( 4 ) and ethyl chaulmoograte ( 5 ). Their structures were determined mainly by using spectroscopic techniques. The absolute configuration at the cyclopentenyl moiety of compound 2 was rationalized by quantum calculations. Base hydrolysis, followed by optical‐rotation comparison, allowed assignment of the configuration of chaulmoogric‐acid moiety of compounds 3 and 5 . Biological assays revealed that compounds 1 – 5 significantly inhibit Mycobacterium tuberculosis (MTB) growth with MIC values of 5.54, 16.70, 4.38, 9.82, and 16.80 μ M , respectively. Compound 3 was found to inhibit the pathway between chorismate and para ‐aminobenzoic acid ( p Aba) with a MIC value of 11.3 μ M , representing a new example of p Aba inhibitor isolated from a natural source. All compounds were not toxic to Candida albicans SC5314 at a concentration up to 100 μ M .