Phenolic compounds of the Australian native herb Prostanthera rotundifolia and their biological activities

- We investigated phenolic compounds of the Australian native herb Prostanthera rotundifolia.
- Eight phenolic acids and flavonoids were identified from the plant.
- Three phenolic acid derivatives were reported for the first time in the genus.
- Methanolic extract of the herb showed moderate antioxidant capacity.
- The extract also showed inhibitory effect on lipase, α-glucosidase and hyaluronidase.

The chemical identity and bioactivities of phenolic components of the Australian native herb Prostanthera rotundifolia were studied. Phenolic compounds were extracted with 80% (v/v) aqueous methanol and purified by liquid chromatography. The antioxidant capacity of the extract and its inhibiting activity against α-glucosidase, pancreatic lipase and hyaluronidase were determined. Phenolic compounds were identified by a combination of HPLC-PDA, LC-high resolution MS (LC-HRMS), LC-tandem MS (LC-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. Compared to spearmint, mint bush showed comparable antioxidant capacity, stronger inhibitory activity on pancreatic lipase and comparable and lower activity on α-glucosidase and hyaluronidase, respectively. Major compounds identified were verbascoside (48.8%), 4-methoxycinnamic acid (36.4%), p-coumaric acid glucose ester (9.2%) and 1-O-β-d-glucopyranosyl sinapate (5.6%), while caffeic acid, p-coumaric acid, hesperidin and naringenin were present in trace quantities. 4-Methoxycinnamic acid, p-coumaric acid glucose ester and 1-O-β-d-glucopyranosyl sinapate were identified for the first time in the genus of Prostanthera.