The antioxidant and antimicrobial activities of methanolic extracts from houseleek (Sempervivum marmoreum L.) leaves

This work is a comparative study of antioxidant and antimicrobial activity of extracts obtained by ultrasound-assisted extraction (UE), classical solvent extraction (CE) and Soxhlet extraction (SE) of Sempervivum marmoreum L. leaves, using methanol. The yield obtained by Soxhlet extraction was also taken to represent the extractive substances (ES) content in the plant material. The extractions were carried out at the room temperature with the ratio of plant material to solvent 1:10g/ml.

Two antioxidant assays, DPPH photometric assay [1] and hydroxyl radical assay [2], were used to evaluate antioxidant activities. The results are presented in Table 1. The agar well-diffusion method was employed for determination of antimicrobial activities of the extracts. Independently of the extraction technique, the methanolic extracts of S. marmoreum showed antibacterial activity against two of the seven tested microorganisms, the mould Aspergillus niger and the yeast Candida albicans. The results indicate that the extract obtained by classical solvent extraction from houseleek leaves, showed better antioxidant, but similar antimicrobial activities, than the extracts obtained by employing two other techniques.

Table 1 Yield of ES and antioxidant activities of S. marmoreum extracts obtained by different extraction techniques

Extraction technique	Yield of ESa	DPPH, EC50, mg/ml b	Hydroxyl radical, EC50, mg/ml
CEc	2.4	0.09±0.01	1.08
UEc	2.3	0.06±0.01	1.26
SEd	2.9	0.12±0.04	ND

^a (g/100g fresh plant material) ^b Mean of three replicates±standard deviation ^c (1:10g/mL, 40min, 25°C) ^d 150min, ND – not determined.

Acknowledgements: Ministry of science and environmental protection, Republic of Serbia projects OI 142073b.

References: [1] Choi C.W. et al. (2002) Plant Sci. 163 (6): 1161–1168. [2] Canadanovic-Brunet J.M. et al. (2004) J Sci Food Agric 85 (2): 265–272.