LC-MS Profiling and Biological Activity of Unexplored Leucas nubica Benth. (Lamiaceae)

Leucas nubica Benth. (Lamiaceae) is an annual herbaceous plant, native to east and northeast tropical Africa. The whole plant is renowned for the treatment of jaundice. The present study aimed at an in-depth phytochemical profiling and evaluation of in vitro antioxidant and enzyme inhibitory potential of methanol–aqueous extract from L. nubica aerial parts. The liquid chromatography–high-resolution mass spectrometry (LC-HRMS) experiment revealed more than 70 secondary metabolites, including carboxylic and phenolic acids, phenylethanoid, iridoid, and lignan glycosides, and flavonoids. The L. nubica extract profile was dominated by the phenylethanoid glycoside verbascoside. All annotated compounds are reported for the first time in the species. The extract actively scavenged DPPH and ABTS radicals (38.8 ± 0.1 and 36.8 ± 0.4 mg TE/g) and showed high CUPRAC (71.1 ± 1.1 mg TE/g) and moderate FRAP (44.9 ± 2.6 mg TE/g) reducing power. The L. nubica extract exhibited high inhibition towards acetylcholinesterase (2.23 ± 0.02 mg GALAE/g), butyrylcholinesterase (2.38 ± 0.04 mg GALAE/g), and tyrosinase (60.7 ± 0.6 mg KAE/g). The obtained results highlight L. nubica extract as a rich source of phenylethanoid glycosides and flavonoids with significant bioactivity and shed light into the phytochemical composition and pharmacological potential of the plant.