Biological activity of constituents of Salvia chamaedryoides

Salvia chamaedryoides Cav. (Lamiaceae) is a Mexican species [1] recently introduced in the Ligurian agricultural market as an ornamental plant, and for extractive purposes [2]. The dichloromethane extract of the aerial parts was investigated for its antimicrobial and hypoglycaemic properties with the aid of bioassay-­‐oriented fractionation. Six new clerodane diterpenes along with six known compounds were isolated, and their structures established by extensive 1D and 2D NMR, and HRESI-­‐TOFMS. For determination of the absolute configuration acetonide derivatives were prepared, and analyzed by comparison of experimental and calculated ECD spectra. The antimicrobial activity was analyzed on several Gram positive (Staphylococcus aureus, S. epidermidis, Enterococcus faecium, E. faecalis, Streptococcus pyogenes, S. agalactiae) and Gram negative (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Moraxella catarrhalis) bacteria, including multidrug resistant strains. The total extract displayed the strongest activity (MIC 2-­‐4 μg/mL), while almost all semi-­‐purified fractions and one pure compound (MIC 32-­‐128 were active on both staphylococci and enterococci. The potential hypoglycaemic properties were evaluated by measuring the inhibitory properties of extract, fractions, and pure compounds against α-­‐amylase and α-­‐glucosidase. Some of the isolated compounds showed a moderate inhibitory activity against α-­‐amylase, while the highest activity was found against α-­‐glucosidase. Three compounds showed IC50 values ranging from 0.20 to 0.29 mM and were stronger inhibitors than the positive control acarbose (IC50=0.45mM). Our results indicate that S. chamaedryoides can be considered as a plant with activity against important Gram positive human pathogens, and may also be helpful to control postprandial hyperglycemia. Keywords: Salvia chamaedryoides, antimicrobial activity, hypoglycaemic activity References [1] Epling C. A Revision of Salvia, subgenus Calosphace. Repertorium Specierum Novarum Regni Vegetabilis., ed. Fedde, F. Vol. 110, Verlag des Repertoriums, Dahlem dei Berlin. Berkley, California: University of California Press; 1939-­‐1940: 154 [2] Cervelli C. Salvie. Caratteristiche, usi e coltivazione. San Remo: Edizioni Ace2; 2011: 49