Yield, pesticide residues, and bioactive compounds of Ugandan Arabica and Robusta coffee flowers

Abstract

• Studied flower yield, pesticides and bioactive compounds of coffee flowers • Robusta coffee trees yielded more flowers than Arabica coffee • Robusta and Arabica flowers had pesticides residues above maximum residue limit • Caffeine was the predominant bioactive compound in Robusta and Arabica flowers Coffee flowers, an underutilized by-product of coffee cultivation, are increasingly becoming popular for their bioactive compounds. However, in Uganda there had been no documentation on their yield, bioactive composition and pesticide residues. A cross-sectional study involving farmers of Arabica coffee (n=50) and Robusta coffee (n=50) was conducted. Flower yield was determined per tree, while pesticides and bioactives in fresh, air-dried, and oven-dried flowers were analyzed using Gas Chromatography-Mass Spectrometry. Phenolics and flavonoids were quantified spectrophotometrically. Data were subjected to descriptive statistics, Chi-square tests, and factorial MANOVA at 5% significance. Robusta trees yielded more flowers (mean ∼618 g/tree) than Arabica (mean ∼462 g/tree). Pesticides were applied more on Arabica than Robusta flowers though both species had some pesticide residues above the maximum residue limit. Caffeine was the main bioactive in both species (Robusta: 665-724 mg/100g; Arabica: 361-407 mg/100g). Additionally, Robusta flowers had squalene while Arabica had n-hexadecanoic acid. Older trees generally had more pesticides but fewer bioactives. Drying significantly (p < 0.05) reduced caffeine contents. Coffee flowers are a good source of bioactive compounds but may be unsafe for human consumption due to presence of pesticide residues. There should be regulated pesticide use and proper post-harvest handling to maximize safety and functional benefits of coffee flowers.