Anti-leukaemic and anti-melanoma activities of homoisoflavonoids from Pseudoprospero firmifolium subsp. natalensis (Hyacinthaceae)

Abstract

Five homoisoflavonoids, (3S)-3,5-dihydroxy-7‑methoxy‑3-(3′,4′-dimethoxybenzyl)-4-chromanone, 1, (3S)-3,5-dihydroxy-7,8-dimethoxy-3-(3′‑hydroxy‑4′‑methoxy)-4-chromanone, 2, (3R)-7,8-dimethoxy-5‑hydroxy‑3-(4′-hydroxybenzyl)-4-chromanone, 3, and (3R)-5‑hydroxy‑7‑methoxy‑3-(3′,4′-dimethoxybenzyl)-4-chromanone, 4, (3S)-3,5,7-trihydroxy-3-(3′‑hydroxy‑4′-methoxybenzyl)-4-chromanone, 5, and a spirocyclic nortriterpenoid, 29‑hydroxy‑15-deoxyeucosterol, 6, were isolated from the bulbs of Pseudoprospero firmifolium subsp. natalensis. Compounds 1, 2 and 5 were isolated previously from P. firmifolium subsp. firmifolium although configurations at C-3 were not established previously. Configurations at C-3 have been confirmed in this work for compounds 1–4 using ECD spectroscopy. The current findings for Pseudoprospero, and most especially of compound 3, indicate that the capacity of the Hyacinthoideae to synthesize homoisoflavonoids evolved prior to the divergence of the three extant tribes (Hyacintheae, Massonieae and Pseudoprospereae) ca. 18.8 Ma ago. Compound 5 displayed activity against two leukemia cell lines SR (GI50 = 0.64 μM) and K-562 (GI50 = 0.86 μM), and the melanoma MDA-MB-435 cell line (GI50=0.41 μM).