Chemical profile and antioxidant activity of geopropolis from Melipona subnitida collected inside and outside the nest

Melipona subnitida (“jandaíra”) is a species of stingless bee endemic to the Caatinga, a dry forest in the northeastern Brazilian semi-arid. Propolis is a product containing beeswax and plant resin. It contains compounds that can be able to prevent health problems by protecting cells against damage by oxidative agents. M. subnitida produces geopropolis, a mixture of propolis with soil. Samples of geopropolis of M. subnitida, one of inside and another outside of the nest from a hive in the municipality of Mossoró (northeastern Brazil) were analyzed by HPLC-PDA-ESI-MS/MS and their antioxidant activity evaluated by the DPPH and β-carotene/linoleic acid methods. Both samples exhibited similar chemical profile, characterized by 26 phenolic compounds, however, the compounds detected were more abundant in sample collected from inside of the nest. They were tentatively characterized as galloyl hexoses, coumaroyl-O-galloyl-hexoses, cinnamoyl-O-galloyl-hexoses, coumaroyl- and cinnamoyl- galloyl hexoses, phenylpropanoyl-O-benzoyl hexoses, flavanones and ellagitannins. Flavonoids, galloyl hexoses, coumaroyl-O-galloyl-hexosides, cinnamoyl-O-galloyl-hexosides and coumaroyl-cinnamoyl-galloyl hexosides were reported previously in this genus, however ellagitannins and phenylpropanoyl-O-benzoyl hexoses are reported for the first time. Comparing the antioxidant activity of the geopropolis samples from inside and outside of the nest, the latter was higher than the former.

亮足无刺蜂（Melipona subnitida，俗称“jandaíra”）是一种特有于巴西东北部半干旱地区卡廷加（Caatinga）干燥森林的无刺蜂物种。蜂胶（Propolis）是一类由蜂蜡与植物树脂构成的蜂产品，其所含活性成分可通过保护细胞免受氧化介质损伤，从而预防机体健康问题。亮足无刺蜂可分泌地蜂胶（geopropolis），即蜂胶与土壤的混合物。本研究针对采自巴西东北部穆索罗市（Mossoró）某蜂箱的巢内与巢外地蜂胶样本，采用高效液相色谱-光电二极管阵列-电喷雾电离串联质谱（HPLC-PDA-ESI-MS/MS）进行成分分析，并通过DPPH法与β-胡萝卜素/亚油酸法对其抗氧化活性进行评价。结果显示，两份样本的化学特征高度相似，均包含26种酚类化合物，但巢内样本的化合物丰度显著更高。经初步鉴定，这些化合物可分为没食子酰己糖、香豆酰-O-没食子酰己糖、肉桂酰-O-没食子酰己糖、香豆酰基与肉桂酰基没食子酰己糖、苯丙酰基-O-苯甲酰基己糖、黄烷酮及鞣花单宁。其中，黄酮类、没食子酰己糖、香豆酰-O-没食子酰己糖苷、肉桂酰-O-没食子酰己糖苷以及香豆酰-肉桂酰-没食子酰己糖苷此前已在该属蜂类中被报道，但鞣花单宁与苯丙酰基-O-苯甲酰基己糖为本研究首次报道。对比巢内与巢外地蜂胶样本的抗氧化活性，巢外样本的抗氧化活性高于巢内样本。