Inhibitory Activity of Propolis Extracts From Stingless Bees (Meliponini) on the Development of Phytopathogenic Fungi: in Vitro Evaluation

Abstract

Objective: The present study aimed to assess the alcoholic extracts of propolis from Tetragona clavipes, Scaptotrigona bipunctata, Tetragonisca angustula, and Melipona quadrifasciata.   Theoretical Framework: There is growing interest in the bioactive metabolites of propolis and honey produced by different species of the group of native stingless bees (NSB) belonging to the Meliponini tribe.   Method: The extracts were prepared in a proportion of 30 g of propolis to 70 mL of 96 % v/v ethanol (1:2). Afterwards, its chemical constituents were characterized by HPLC. A PDA medium was used to evaluate the antifungal activity, with the extracts added to the melting medium (55 °C) in different concentrations. The effect of increasing concentrations (1.6 %, 3.2 %, 6.4 %, and 12.0 % v/v) of extracts on the mycelial growth of the fungi Sclerotinia sclerotiorum, Fusarium sp., Colletotrichum gloeosporioides, Botrytis cinerea, and Botryosphaeria sp. was evaluated. Fungal development was determined by measuring mycelial diameter on the 14th day of inoculation.   Results and Discussion: The antioxidant activity and the contents of flavonoids and phenolic compounds were identified in all samples of propolis extracts from ANSF. The T. clavipes propolis extract had the highest content of phenolic compounds (5,593 mgEAG·100 mL-1). Among the chemical compounds, naringin, gallic acid, hesperidin, and ferulic acid were identified in greater quantities. The fungi evaluated in this work were partially inhibited by most SNB alcoholic extracts, mainly at concentrations of 1.6 % and 3.2 % v/v compared to the control treatment (ethanol 96 % v/v). Changes in the hyphal network and the reduction or absence of conidia were also observed when combined with different alcoholic propolis extracts and the control with 96 % v/v ethanol.   Research Implications: The results demonstrate that the chemical components of the alcoholic extracts of NSB propolis have the potential for controlling phytopathogenic fungi of agricultural interest.   Originality/Value: This study contributes by assessing and highlighting the potential applications of NSB as natural products in the alternative control of phytopathogenic fungi of agricultural interest.