The presence of Fabaceae in the pollen profile of propolis produced in northeastern Brazil

ABSTRACT Propolis is a resin-like substance composed mainly of resin, wax, essential oils, pollen grains and specific plant parts collected by the honeybee Apis mellifera, which mixes them with fluids they secrete. The components and chemical properties of propolis vary among regions. Therefore, in order assess variation in the botanical composition of propolis, 26 samples of propolis (brown, red, and green) produced throughout northeastern Brazil were analyzed by acetolysis specifically adapted for propolis. In total, 196 pollen types were recorded, representing 123 genera and 47 families, with types of Fabaceae and Rubiaceae being present in 100 % of the samples. Fabaceae was the richest group with 49 pollen types, followed by Malvaceae (10 types), particularly related to the high frequencies of Mimosa pudica (84.62 %), Alternanthera, Borreria verticillata, and Myrcia (80.77 %). Remarkably, 34 % of the pollen types with frequencies above 50 % belonged to Fabaceae, even though this family has been traditionally regarded as less important with regard to propolis production, given that most of its included taxa are classified as polliniferous or nectariferous. Similarity analyses revealed clusters of propolis samples that share pollen types associated with plants having apiculture potential.摘要：蜂胶（propolis）是一类树脂状物质，主要由西方蜜蜂（Apis mellifera）采集的树脂、蜡质、精油、花粉粒及特定植物组织，混合自身分泌的体液后形成。蜂胶的组分与化学性质因地域而异。为评估蜂胶的植物源组成差异，研究人员对巴西东北部地区产出的26份棕、红、绿三色蜂胶样本，采用适配于蜂胶的乙酰解（acetolysis）方法开展分析。本次研究共记录到196种花粉类型，隶属于47科123属；其中豆科（Fabaceae）与茜草科（Rubiaceae）的花粉类型在全部样本中均有检出。豆科是物种最丰富的类群，包含49种花粉类型，其次为锦葵科（Malvaceae，10种），其中含羞草（Mimosa pudica）的检出频率高达84.62%，莲子草属（Alternanthera）、轮生博雷尔草（Borreria verticillata）以及香桃木属（Myrcia）的检出频率均为80.77%。值得注意的是，检出频率超过50%的花粉类型中有34%隶属于豆科；尽管传统观点认为该科在蜂胶生产中重要性较低，因其多数类群仅被归为产粉植物或泌蜜植物。相似性分析结果显示，不同蜂胶样本可聚为若干类群，各类群共享的花粉类型均与具备养蜂（apiculture）潜力的植物相关。