Antioxidant and complement modulating activities of five essential oils

Abstract

(LE) (Citrus limon (L.) Burman fil.), rosemary (RO) (Rosmarinus officinalis L.), Spanish oregano (SO) (Thymbra capitata Griseb.) and thyme (TH) (Thymus zygis L.), were investigated for their activity on the complement system and their antioxidant properties by in vitro assays. Oils were obtained from commercial sources. Their main components (identified by GC-MS and quantified by GC-FID) were as follow: eugenol (86.2%) for CL; limonene (71.6%), s-pinene (12.2%) and γ-terpinene (6.9%) for LE; 1,8 cineole (49.7%), α-pinene (9,9%) and camphor (9,6%) for RO; carvacrol (73,5%) for SO, and thymol (56,6%) and p-cymene (28,4%) for TH. Free radical scavenging activity was evaluated using 1,1-diphenyl2-picrylhydrazyl (DPPH) [1]. The activity on classical complement pathway was determined in human serum by hemolytic assay [2]. Positive control was quercetin for both assays, showing an IC =10.5±4.6µg/mL for the DPPH test and an IC =33.7±4.3µg/mL for the assay on the complement system. Only CL showed antioxidant activity in the DPPH (IC =13.2±2.9µg/mL), indicating that this oil has free radical scavenging activity. Results on inhibition of the classical pathway of the complement system, showed that TH and CL have similar weak activity, with IC =61.4±10,6µg/mL and 72.7±4.1µg/mL, respectively. SO, RO and LE showed no inhibitory effect on the complement system activated by the classical pathway. In conclusion, from the five oils tested, the clove essential showed the best combination of free radical scavenging and complement inhibitory activities.