In this paper, we report the influence of the extraction process on the flavonoid content obtained from leaves of C. quercifolius and its antioxidant activity. A factorial design 2² was performed, using temperature and agitation as independent variables. Qualitative and quantitative analyzes of the extracts were performed by HPLC-DAD. Rutin and apigenin were identified in the extracts and chosen as analytical markers. Pareto chart and Surface response plots suggested that rutin content was increased up to 3.93 times when temperature was employed during the extraction process. However, apigenin content was significantly reduced in the method whose temperature or agitation were used (p<0.05). A higher antioxidant activity was observed in extracts whose rutin extraction was favored, suggesting that this flavonoid contributes at least in part to the antioxidant potential of the species.

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BackgroundLeonotis nepetifolia (Family Lamiaceae) is a medicinal plant from which the flavonoid cirsiliol with sedative, hypnotic, anti-inflammatory and cytotoxic activity has been extracted.MethodsSeedlings were cultivated under different levels of shade in native or fertilized modes. The content of cirsiliol was measured monthly by high-performance liquid chromatography and the total phenolic content by the Folin-Ciocalteu method. Monitoring of growth was carried out with the weekly measurement of height until the stabilization of growth.ResultsThe application of fertilizing and/or shading does not alter significantly the cirsiliol content. However, this content varies throughout the year, reaching the peak production in the summer, independently of the treatment applied. This same profile, with production in the summer, was also verified for phenolic compounds, reaching 58.15 ± 9.35 mg of equivalents of gallic acid per g of extract in the summer, content 1.84 times greater than the content verified in winter (31.56 ± 4.09 mg of gallic acid/g of extract). Although shading and fertilizing had no effect on cirsiliol content, the results also showed a positive influence on the height and biomass of the plant, which can causes a higher yield of extractable material.DiscussionBiotic and abiotic stresses are able to increase or decrease the production of secondary metabolites, including phenolic compounds in medicinal plants and, as the stress response is peculiar to each species, cultivation studies become necessary. The present study reports by the first time the influence of shading, fertilizing and seasons in cirsiliol content in L. nepetifolia. Among analyzed variables, the seasons showed a larger influence in expression of cirsiliol and among seasons, our results showed that the summer is the ideal season for collections. In summer, the photoperiod is larger than in other seasons of the year and due to that, the plants need greater protection against the long photoperiod. For this, the plants increase the production of phenolic compounds as observed in this study. Although they do not influence the production of cirsiliol, the shading and nutrients in soil favor growth and leaf area of several plants, explaining, thus, the higher height and biomass obtained.