Plectranthus species are rich in abietane-type diterpenes, such as royleanones, which can justify their traditional use for a wide range of complaints including cancer and skin disorders. Therefore, the aim of this work is to study the phytochemistry and biological activity of P. hadiensis (Forssk.) Schweinf. ex Sprenger. var. hadiensis leaves, stems and whole plant acetone and methanol extracts.

Air-dried P. hadiensis leaves, stems and whole plant were extracted in acetone and methanol using the ultrasound-assisted extraction method. The phytochemical study was carried out using different chromatographic techniques and their chemical composition studied and compared. The results indicate a great difference between the acetone extracts from leaves and stems. 7α-acetoxy-6β-hydroxyroyleanone (Roy) was found to be the major compound in the acetone leaves extract but not in the stems extract. P. hadiensis acetone leaves and whole plant methanol extracts were screened for their antioxidant, antimicrobial, general toxicity, and cytotoxic activities. The antimicrobial activity was higher in acetone extract than in methanol extract, while the acetone leaves extract had the highest general toxicity. Roy isolated from the acetone leaves extract was further studied. It was about 12 times more cytotoxic against the MDA-MB-231S cancer cell lines than the corresponding extract.

Currently, phytochemical studies on the acetone stems, methanol whole plant of P. hadiensis var. hadiensis and P. hadiensis var. tomentosus leaves and stems methanol, acetone and ionic liquid extracts are ongoing to elucidate the main compounds that may be responsible for the biological activity.

Acknowledgements: This work was supported in part by FCT – Fundacão para a Ciência e Tecnologia grants PEst- OE/SAU/UI4013/2014, UIDP/04567/2020, UIDB/04567/2020, CBIOS/COFAC/FIPID/1/2019 and UIDP/04567/2020. E.M.D-M gratefully acknowledges being the recipient of a predoctoral FPU 2019 fellowship from University of Alcalá.