Jean Noël Nyemb*, Alembert T Tchinda, Emmanuel Talla, Emmanuel B Nanga, David T Ngoudjou, Céline Henoumont, Sophie Laurent, Jamshed Iqbal and Joseph T Mbafor
A new cerebroside (2R)-2-hydroxy-N-[(Z,2S,3S,4R)-1-O-β-D-glucopyranosyl-3,4-dihydroxynonadec-8-en-2-yl] nonacosanamide (1) was isolated from the wood of roots of V. paradoxa along with six known compounds including catechin (2), quercetin (3), spinasterol 3-O-β-D -glucopyranoside (6), gallic acid (7) and a mixture of β-sitosterol (4) and stigmasterol (5). The structure of the new compound was established by 1D (1H and 13C NMR) and 2D NMR (COSY and HSQC) spectroscopy, extensive mass spectrometry and by comparison with published data. The antibacterial, α-glucosidase and alkaline phosphatase (AP) inhibitory activities of all the pure compounds were evaluated. The antibacterial activities were evaluated against three gram negative bacteria (Escherichia coli; Salmonella typhimurium and Pseudomonas aeruginosa) while APs inhibitory activities were evaluated on h-TNAP and h-IAP. Significant antibacterial activity was recorded for quercetin (3) against P. aeruginosa. Most of the compounds except 1 and 6 were found to be inhibitors of α-glucosidase. The highest inhibitory potential being recorded for quercetin (3) with IC50 value of 4.30 ± 0.01 μM, 55 fold higher than the standard drug acarbose (IC50=234.6 ± 2.01 μM). All tested compounds exhibited moderate inhibitory activities against APs. h-TNAP inhibitory values were ranged between 41.24 ± 1.33 μM and 312.54 ± 6.44 μM while h-IAP inhibitory values were in the range of 47.95 ± 0.35 μM and 777.47 ± 18.55 μM. Quercetin (3) was found to be the most active h-IAP inhibitor (IC50=47.95 ± 0.35 mM), whereas, spinasterol 3-O-β-D-glucopyranoside (6) was found to be the most active h-TNAP inhibitor (IC50=41.24 ± 1.33 mM). The new compound (1) showed moderate inhibition on h-IAP (78.11 ± 3.70 μM) and on h-TNAP (88.84 ± 2.70 μM).