The effect of different extraction techniques on the composition and antioxidant activity of cherry laurel (Prunus laurocerasus) leaf and fruit extracts

Abstract

The effects of different extraction techniques, including microwave and ultrasound assisted, classical and Soxhlet extraction, on the extractive yield, phenolic composition and DPPH-scavenging activity of cherry laurel leaf and fruit extracts were compared. The total phenolic and flavonoid content was determined according to the Folin–Ciocalteu and aluminum chloride methods, respectively. The antioxidant activity of the methanolic extract was evaluated according to the DPPH assay, while the phenolic composition was determined using the HPLC. The results showed that the extracting techniques and nature of the plant material significantly affect the extractive yield and phenolic composition of the extracts. The different plant material showed significant differences in the total phenolic content (119.4±1.1 to 36.2±0.6mg of gallic acid/g of dry extract), the total flavonoid content (66.6±0.2 to 12.9±0.2mg of rutin/g of dry extract) and the antioxidant activity (108.1±7.7 to 271.2±7.6μg/ml) (p<0.05). The highest extractive yields for both plant materials (leaves and fruit) were obtained by the Soxhlet extraction, while the extracts obtained by microwave-assisted extraction contained the highest amount of phenolic and flavonoid compounds and exhibited the best antioxidant activity. High correlations between phenolic compositions and antioxidant activities of both analyzed extracts were observed. Independently of the plant material and technique applied, chlorogenic acid was the major phenolic compound in all the extracts. o-Coumaric acid, quercetin 3-glucoside, luteolin 7-glucoside, apigenin 7-glucoside, kaempferol 3-glucoside, and naringenin were detected in the leaf extracts for the first time, while the presence of vanilic acid, caffeic acid, and rutin was confirmed in the fruit extracts.