PHENOLIC DERIVATIVES AND ANTIOXIDANT ACTIVITY OF POLAR EXTRACTS FROM Bauhinia pulchella

A tea made with the leaves or stem bark of Bauhinia pulchella Benth (Fabaceae) is used in the treatment of diabetes. Ethanol (EEF) and aqueous (EAF) extracts were obtained from the leaves and the antioxidant and citotoxic activities were tested, as well as quantify the content of flavonoids and phenolic compounds (TPC). EEF and EAF showed similar profiles by HPLC, with the presence of three compounds. Column chromatography reverse phase (C18) and Sephadex LH-20, followed by semi preparative HPLC-C18 of EAF resulted in three flavonoids. Their structures were identified by 1H and 13C NMR as myricitrin (1), quercitrin (2) and afzelin (3). In assay of determination of reactive substances to thiobarbituric acid (TBARS), with DPPH, ABTS and nitric oxide (NO•) free radicals, EAF showed antioxidant potential higher than the EEF. This is the first report of the occurrence of the flavonoids 1-3, in the species B. pulchella. EEF and EAF were inactive in the cytotoxicity assays. In short, the polar extracts from the leaves of B. pulchella proved to be promising sources of biomolecules phenolic, with antioxidant potential, which may, in the future, be used as chemical markers for species and validation of therapeutic use.

美丽羊蹄甲（Bauhinia pulchella Benth，豆科Fabaceae）的叶片或茎皮所制备的茶饮，常用于糖尿病的治疗。本研究从该植物叶片中提取得到乙醇提取物（EEF）与水提取物（EAF），并对二者的抗氧化活性与细胞毒性进行了检测，同时定量分析了其中的黄酮类化合物与总酚类物质（TPC）含量。高效液相色谱（HPLC）分析显示，EEF与EAF的色谱图谱相似，二者均含有三种化合物。通过反相柱色谱（C18）与葡聚糖凝胶LH-20层析，结合半制备型高效液相色谱-C18对EAF进行分离纯化，最终得到三种黄酮类化合物。借助氢谱（¹H NMR）与碳谱（¹³C NMR）对其结构进行鉴定，分别为杨梅苷（1）、槲皮苷（2）与阿福豆苷（3）。在硫代巴比妥酸反应物质（TBARS）、1,1-二苯基-2-三硝基苯肼（DPPH）、2,2'-联氮-双(3-乙基苯并噻唑啉-6-磺酸)（ABTS）以及一氧化氮自由基（NO•）的清除实验中，EAF的抗氧化活性均高于EEF。本研究首次报道了在美丽羊蹄甲中存在黄酮类化合物1-3。细胞毒性实验结果显示，EEF与EAF均无细胞毒性活性。综上，美丽羊蹄甲叶片的极性提取物被证实为极具潜力的酚类生物分子来源，其具备抗氧化活性，未来可作为该物种的化学标记物以及治疗用途验证的参考依据。