No abstract

The genus Hibiscus thrives in a variety of climates and produces a diversity of natural compounds with bioactive properties. We have studied the chemical composition and the in vivo antioxidant properties of Hibiscus tiliaceus L. methanolic flower extract, as well as its mutagenic/antimutagenic effects. Vitamin E and some stigmasterol derivatives that might confer an antioxidant effect to the extract were present. Treatment with this extract protected several Saccharomyces cerevisiae strains defective in antioxidant defenses against H2O2 and t-BOOH cytotoxicities, showing a clear antioxidant activity. The effect is the same for all strains used, independent of the antioxidant defense disrupted, suggesting that protection may be due to molecules that act as versatile and wide spectrum nonenzymatic antioxidants, such as vitamins or phytosterols. The extract was not mutagenic in either Salmonella typhimurium or S. cerevisiae and showed a significant antimutagenic action against oxidative mutagens in S. cerevisiae.

The objective of this work was to carry out a comparative study of conventional extraction methods (maceration and Soxhlet) versus sonication in the case of the flowers of Hibiscus tiliaceus, collected at the Santa Catarina swamps (in the south of Brazil), using three solvents with different degrees of polarity. All extracts were analyzed by GC/MSD. For all the extraction procedures used, the initial extraction was performed with hexane with the aim of completely removing non‐polar compounds (mainly hydrocarbons). This procedure will ensure that the compounds of real interest, i. e., those possessing pharmacological properties, can be better characterized. Variation of solvent type is found to have a much greater effect than variation of the extraction method. The total analysis time and the total amount of solvent are clearly reduced on use of the best method, i. e. sonication. The best sonication results were obtained with an extraction time of 160 minutes using methanol as extraction solvent. The solvent used determines the nature of the compounds extracted. Polar compounds are satisfactorily extracted by using highly polar solvents. Among the compounds identified, saturated hydrocarbons from 25 to 33 carbon atoms, esters, and carboxylic acids of high molecular weight, as well as some steroid structures are highlighted.

The influence of several experimental parameters on the ultrasonic extraction of Hibiscus tiliaceus L. flowers were investigated: extraction time, solvent polarity, sample amount, solvent volume and sample particle size. It was concluded that the most influential variables were extraction time and solvent polarity. The optimized procedure employed 5 g of ground flowers, 150 mL of methanol and 140 min of extraction. The extracts were fractionated using preparative silica columns and the resulting fractions were analyzed by GC/MS. Some saturated hydrocarbons, fatty acids, fatty acid methyl esters, phytosterols, and vitamin E were identified in the plant extracts.