Biological activity of 6,7-dehydroroyleanone derivatives from Plectranthus aliciae

Plectranthus genus (Lamiaceae) is known to be rich in bioactive abietane royleanone-type diterpenes, such as 6,7-dehydroxyroyleanone (1, [Fig. 1]), which have been previously found in P. madagascariensis (var. aliciae Codd). This abietane royleanone presents moderate to significant cytotoxic activity against several cancer cell lines. Moreover, 1 has one hydroxyl group suitable for derivatization that can be explored to enhance the cytotoxic activity of lead compound 1. Based on this, the aim of the present work is to explore the obtention of 1, from P. aliciae aliciae (Codd) van Jaarsv. & T.J.Edwards., a subspecies of P. madagascariensis to be further used in the preparation of new derivatives with enhanced biological activities.

Fig. 1 Structure of 6,7-dehydroxyroyleanone (1) and semi-synthetic ester derivatives (2, 3 and 4).

P. aliciae leaf hydrodistillation using Clevenger equipment was performed, affording the essential oil (EO). 1 was assessed as the major compound of the EO, by HPLC-DAD, which was isolated and used as a scaffold for esterification reactions. It was possible to obtain three new acyl derivatives (2 – 4, [Fig. 1]), with overall good yields (86 – 95%). Regarding the biological activity screening, the semi-synthetic derivatives (2 – 4) improved the antioxidant activity and the cytotoxic activity in MCF-7 and NCI-H460 cancer cell lines, when compared to 1. Amazingly, the new esters (2 – 4) showed a promising anti-inflammatory activity, in the range of 16 to 53 times more than 1, and also higher than the one of the positive control (dexamethasone). Currently, the mechanism of action and security of the potential anti-inflammatory derivatives are under evaluation.

Publikationsverlauf

Artikel online veröffentlicht:
16. November 2023