Antibacterial activity of abietane diterpenes from the roots and hairy roots of Salvia corrugata Vahl.

The major compounds of the surface extract of the aerial parts of Salvia corrugata Vahl., demethylfruticuline A (1) and fruticuline A (2), showed significant antibacterial activity [1] and inhibited in vitro the synthesis of biofilm of multi-resistant clinical strains of Staphylococcus and Enterococcus [2]. 7β-acetoxy-20-hydroxy-19,20-epoxyroyleanone and 7β-ethoxy-6β,20:19,20-diepoxyroyleanone, isolated from in vitro shoots [3] were active at various degrees against the same bacterial genera.

The methanolic extract of the roots and the twelve semi-purified fractions obtained by its chromatographic separation were tested against several multidrug resistant clinical strains also of marine origin (S. aureus, S. epidermidis, S. capitis, S. haemolyticus, S. hominis, S. lugdunensis, S. saprophyticus, S. simulans, S. warneri, E. faecalis, E. faecium, E. gallolyticus, E. durans, E. avium) displaying MIC values ranging from 4 to >128 μg/mL. Horminone (3), 7-O-acetylhorminone (4) and 7-O-methylhorminone were isolated. 3 and 4, obtained in suitable amounts, showed MIC values ranging from 4 to 64 μg/mL against the same bacterial strains.

Hairy roots were induced from the leaves of S. corrugata, obtained through in vitro culture of nodal segments of wild plants, transformed with Agrobacterium rhizogenes strain (MTCC532). The methanolic extract did not contain 1 and 2 and it was moderately active against multi-resistant clinical strains of E. faecalis and E. faecium displaying MIC values ranging from 64 to 128 μg/mL. Four semi-purified fractions obtained by chromatographic separation showed MIC values ranging from 4 to 16 μg/mL. The fractions showed lower activity against Staphylococci. Ferruginol and the new 19[4→3]abeo-O-demethyl-14-hydroxy-cryptojaponol (5) were isolated from fraction III. 5 showed a wide range of activity against Enterococci (MIC values 1 - 128 μg/mL).

• References

• 1 Bisio A, Romussi G, Russo E, Cafaggi S, Schito AM, Repetto B, De Tommasi N. Antimicrobial activity of the ornamental species Salvia corrugata, a potential new crop for extractive purposes. J Agric Food Chem 2008; 56: 10468-10472
• 2 Schito AM, Piatti G, Stauder M, Bisio A, Giacomelli E, Romussi G, Pruzzo C. Effects of demethylfruticuline A and fruticuline A from Salvia corrugata Vahl. on biofilm production in vitro by multiresistant strains of Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis . Int J Antimicrob Agents 2011; 37: 129-134
• 3 Bisio A, Fraternale D, Schito AM, Parricchi A, Dal Piaz F, Ricci D, Giacomini M, Ruffoni B, De Tommasi N. Establishment and analysis of in vitro biomass from Salvia corrugata Vahl. and evaluation of antimicrobial activity. Phytochemistry 2016; 122: 276-285