GC-MS and LC-TOF-MS profiles, toxicity, and macrophage-dependent in vitro anti-osteoporosis activity of Prunus africana (Hook f.) Kalkman Bark.

Osteoporosis affects millions of people worldwide. As such, this study assessed the macrophage-dependent in vitro anti-osteoporosis, phytochemical profile and hepatotoxicity effects in zebrafish larvae of the stem bark extracts of P. africana. Mouse bone marrow macrophages (BMM) cells were plated in 96-well plates and treated with P. africana methanolic bark extracts at concentrations of 0, 6.25, 12.5, 25, and 50 µg/ml for 24 h. The osteoclast tartrate-resistant acid phosphatase (TRAP) activity and cell viability were measured. Lipopolysaccharides (LPS) induced Nitrite (NO) and interleukin-6 (IL-6) production inhibitory effects of P. africana bark extracts (Methanolic, 150 µg/ml) and ß-sitosterol (100 µM) were conducted using RAW 264.7 cells. Additionally, inhibition of IL-1ß secretion and TRAP activity were determined for chlorogenic acid, catechin, naringenin and ß-sitosterol. For toxicity study, zebrafish larvae were exposed to different concentrations of 25, 50, 100, and 200 µg/ml P. africana methanolic, ethanolic and water bark extracts. Dimethyl sulfoxide (0.05%) was used as a negative control and tamoxifen (5 µM) and dexamethasone (40 µM or 80 µM) were positive controls. The methanolic P. africana extracts significantly inhibited (p < 0.001) TRAP activity at all concentrations and at 12.5 and 25 µg/ml, the extract exhibited significant (p < 0.05) BMM cell viability. NO production was significantly inhibited (all p < 0.0001) by the sample. IL-6 secretion was significantly inhibited by P. africana methanolic extract (p < 0.0001) and ß-sitosterol (p < 0.0001) and further, chlorogenic acid and naringenin remarkably inhibited IL-1ß production. The P. africana methanolic extract significantly inhibited RANKL-induced TRAP activity. The phytochemical study of P. africana stem bark revealed a number of chemical compounds with anti-osteoporosis activity. There was no observed hepatocyte apoptosis in the liver of zebrafish larvae. In conclusion, the stem bark of P. africana is non-toxic to the liver and its inhibition of TRAP activity makes it an important source for future anti-osteoporosis drug development.

A Micropropagation Protocol for the Endangered Medicinal Tree Prunus africana (Hook f.) Kalkman: Genetic Fidelity and Physiological Parameter Assessment.

Prunus africana is an endangered medicinal plant and hence new propagation methods are urgently required to increase its populations. Unfortunately, propagation through seeds is challenging due to its long flowering cycle and recalcitrant seeds. We developed a protocol for micropropagation using nodal segment explants. A woody plant medium supplemented with vitamins, 15 g L-1 sucrose, and 1.0 mg L-1 6-benzylaminopurine (BAP) supported the optimum rate (100%) of axillary shoot initiation. Supplementation with 15 g L-1 sucrose and 1.5 mg L-1 indole-3-acetic acid (IAA) provided the optimum rate (75%) of root initiation. Rooted plantlets were successfully planted in sterilized horticultural soil containing perlite (2:1 v/v) and the survival rate was 98% following acclimatization. The photosynthetic rate assessed using FlourPen FP110 series showed that the ratio of variable fluorescence to maximum fluorescence mean value for in vitro regenerated P. africana (0.830 ± 0.0008) was similar to that of the maternal P. africana plant (0.825 ± 0.005), indicating similarity in their photosynthetic performance; a pivotal process for growth and development. The Fourier transform near-IR (FT-NIR) spectrometer analysis of the in vitro regenerated and the maternal P. africana plant samples exhibited homogeneity in the absorbance peaks at 8,273, 6,344, and 4,938-4,500 cm-1 associated with lipids, starch, and proteins. The genetic fidelity of regenerated plants was confirmed using the randomly amplified polymorphic DNA (RAPD) technique. Our protocol is suitable for use in large-scale P. africana to meet the increasing demands for it in the global market.