Cytotoxicity of endemic Haplophyllum megalanthum Bornm. and its newly isolated alkaloids and lignans

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In this study, two previously unreported lignans [4′-O-demetylsuchilactone-8′-ol (1), 7-O-(3-methyl-2,3-dihydroxy-butyl)isodaurinol] (2), four new alkaloids (haplomegalanthine (3), megalantin (4), megalanthamide (5), glycoisohaplopine (6) and thirty-five known compounds (7–41) were isolated from Haplophyllum megalanthum Bornm. (Rutaceae). Pinoresinol (23), epipinoresinol (24), indole-3-carbaldehyde (29), N-[2-(4-hydroxyphenyl)ethyl]-3-methylbut-2-enamide (34), 7,8-dimethoxyfuroquinoline-4-one (35), cis-khellactone (36), 4,4′-dihydroxy-3,3′,9-trimethoxy-9,9′-epoxylignan (37), ulopterol (39) and trans-decursidinol (40) were identified for the first time in the genus Haplophyllum. Also, 4′-O-demethylsuchilactone (16) and N-(4-hydroxyphenethyl)benzamide (32) were found for the first time within the family Rutaceae. Structures of the compounds were elucidated by the use of HRMS, UHPLC-MS and 1D/2D NMR analyses. Furthermore, cytotoxic activity of the crude extract and previously unreported compounds (1–3, 5, 6) on colon cancer cell line HT29 were tested by the MTT method. IC50 values were determined for these five compounds and the crude extract as 18.48 ± 0.94 μg/ml, 52.62 ± 7.27 μg/ml, 23.15 ± 6.70 μg/ml, 21.45 ± 2.48 μg/ml, 5.06 ± 0.19 μg/ml and 2.82 ± 0.012 μg/ml, respectively.The present report is the first detailed phytochemical investigation of the title plant pointing out that it comprises a rich source of diverse chemical constituents including new compounds with promising cytotoxic activity.