Effect of seasonal variation on the chemical composition and antioxidant and antifungal activities of Convolvulus althaeoides L. leaf extracts

The composition of polyphenols, chlorophylls and carotenoids of eight extracts of Convolvulus althaeoides L. leaves, harvested in two different seasons, winter and spring, and extracted by hot extraction method using four solvents (dichloromethane, chloroform, ethyl acetate and ethanol) with increasing polarity, were evaluated along with their antioxidant and antifungal activities. Qualitative and quantitative variations were observed in the composition based on two different high performance liquid chromatography systems, liquid chromatography-photodiode array detection coupled to either atmospheric pressure chemical ionization mass spectrometry or to electrospray ionization mass spectrometry, permitting the identification of 22 polyphenols, 11 chlorophyll derivatives and 10 carotenoid compounds. Polyphenolic compounds were predominant in extracts from leaves collected in winter, whereas pigments were predominant in the spring collections. Antioxidant activities of the extracts were determined by DPPH radical scavenging method, revealing a half inhibition concentration (IC50) ranging from 0.1369 ± 0.0272 mg g−1 to 0.432 ± 0.0018 mg g−1, with no correlation to seasonal fluctuation. Concerning antifungal assays, ethyl acetate and ethanol extracts have been shown to be the most active against dermatophytes (T. rubrum, T. menthagrophytes, M. canis), with inhibiting percentages reaching 100% with 50 mg mL−1. Moreover, ethyl acetate and ethanol extracts showed a maximum inhibition potential with minimum inhibitory/fungicidal concentrations ranging from 0.78 to 6.25 mg mL−1 on Candida spp. cultures. The winter collect of these extracts showed an inhibitory effect of 90% on Candida albicans germ tubes formation, at a concentration of 3.1 mg mL−1. In conclusion, seasonality seems to influence the quality and the quantity of natural substances from leaves of C. althaeoides L., which have major importance on the antioxidant and the antifungal effectiveness.