Blighia sapida Köenig (Sapindaceae), known commonly as ackee or akee, is a plant indigenous to equatorial Africa and cultivated in the West Indies. The fruit aril of ackee is edible, and is an important ingredient in a popular Jamaican codfish dish. The pod and the seed of the fruit are discarded, and are a byproduct in the ackee canning industry, accounting for almost 70% (w/w) of the ackee fruit. Three new triterpene saponins, 3- O-[α-
L
-arabinopyranosyl-(1→4)-3-
O-acetyl-β-
D
-glucopyranosyl-(1→3)-α-
L
-rhamnopyranosyl-(1→2)-α-
L
-arabinopyranosyl] hederagenin (
1) (blighoside A), 3-
O-[α-
L
-arabinopyranosyl-(1→4)-3-
O-acetyl-β-
D
-glucopyranosyl-(1→3)-α-
L
-rhamnopyranosyl-(1→2)-α-
L
-arabinopyranosyl] oleanolic acid (
2) (blighoside B), and 3-
O-[4,6-
O-diacetyl-β-
D
-glucopyranosyl-(1→3)-α-
L
-rhamnopyranosyl-(1→4)-3,6-
O-diacetyl-β-
D
-glucopyrano-syl-(1→3)-α-
L
-rhamnopyranosyl(1→2)-β-
D
-xylopyranosyl-(1→3)-β-
D
-xylopyranosyl] oleanolic acid (
3) (blighoside C), and two known steroids, stigmasta-5,22-dien-3-ol and stigmasta-5,22-dien-3-
O-glucopyranoside, were isolated from the EtOAc fractions of
B. sapida pod. Blighosides A-C, which are monodesmosidic saponins, exhibited significant cytotoxic effect on the growth of ER
- MDA-MB-453 (Her2 overexpressing) human breast cancer cells at IC
50 = 6.9 μM (
B), 10.0 μM (
C), and 10.3 μM (
A), as compared to actein (IC
50 = 14.8 μM; 10 μg/ml). The
n-butanol and EtOAc fractions of the ackee pod also exhibit inhibitory effects at IC
50 = 20 μg/ml and 43 μg/ml, respectively.
Additionally, in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical assay, the EtOAc fractions of B. sapida pod and seed showed strong DPPH antioxidant activities, and high total phenolic and flavonoids content. Through activity-guided fractionation of selected fractions, six known polyphenolic antioxidants, methyl gallate (1), quercetin 3-O-β-glucopyranoside (isoquercitrin) (2), cyanidin 3-O-β-glucopyranoside (3), 3,4-dihydroxybenzoic acid (protocatechuic acid) (4), gallic acid (5), ellagic acid (6), and quercetin (7) were isolated and identified from the EtOAc fractions of the ackee pod for the first time. These polyphenolic antioxidants have strong radical scavenging properties and may contribute to the high activity of the ackee pod.
