Sucrose esters of aryldihydronaphthalene-type lignans, and antitumor activity of extracts of Moltkiopsis ciliata (Forssk.) aerial parts

Abstract

One new compound (3f-[(7′R,8′R)-4,4′-dihydroxy-5-methoxy-2,7′-cycloligna-7-en-9-methoxycarbonyl, 9′-carbonyl-O-] -β- D-fructofuranosyl- (2→1)-α- D-glucopyranoside) (Moltkiopsin A) (2) was isolated and identified from the extract of aerial parts of the wild Egyptian plant Moltkiopsis ciliata (Frossk.), family Boraginaceae, for the first time, along with two aryldihydronaphthalene lignans 3f→9′:6f→9-[(7′R,8′R)-4,4′- dihydroxy-3,3′,5-trimethoxy-2,7′-cycloligna-7-en-9,9′-dicarbonyl]-6g-acetyl-α-D-gluco pyranosyl-(1→2) -β-D-fructofuranoside (Trigonotin A) (1) which was reported for the first time from this plant species and a known compound 3f→9′:6f→9-[(7′R,8′R)-4,4′- dihydroxy-3,3′,5-trimethoxy-2,7′-cycloligna-7-en-9,9′-dicarbonyl]-α-D-gluco pyranosyl - (1→2)- β-D- fructofuranoside (Trigonotin C) (3). These compounds were separated and purified using different chromatographic techniques and their structures were elucidated by extensive 1D (1H and 13C NMR), and 2D NMR (COSY, HSQC, and HMBC), besides ESI-MS spectral methods. Extracts were screened as antioxidant, antitumor and antibacterial. The different extracts showed moderate to strong antioxidant capacities in DPPH assays. Ethyl acetate, methylene chloride and crude methanol extracts exhibited the most significant free radicals scavenging activity when compared to the standard antioxidant vitamin C. Hexane and butanol fractions showed the highest cytotoxicity against the cancer cell lines HepG2 and MCF-7.