Quantitative UPLC-MS/MS analysis of obliquumol from Ptaeroxylon obliquum (Thunb.) Radlk. extracts and biological activities of its semi-synthesised derivative ptaeroxylinol

•UPLC-MS/MS method developed to quantify obliquumol concentration in P. obliquum acetone extracts.•Ptaeroxylinol had MIC values as low as 8 µg/mL and 16 µg/mL against C. albicans ATCC 10,231 and cryptococcus neoformans respectively.•Ptaeroxylinol had some antimycobacterial activity with MIC value of 62.5 µg/mL against both M. bovis BCG and M. fortuitum.•Ptaeroxylinol had low toxicity against both vero and human liver (C3A) cells with IC50 = 85.7 and 126.51 µg/mL respectively.