Effect of drying conditions on the preservation of selected bioactive compounds in Moringa oleifera aqueous extract: acetic acid, butyric acid, γ-aminobutyric acid, salicin, and glycine.

BACKGROUND: Medicinal plants like Moringa oleifera, which possess high moisture content and microbial susceptibility, require prompt and efficient drying as a vital post-harvest step to ensure product stability and quality. This process is crucial for maintaining the plant's sensory attributes and preserving secondary metabolites that are fundamental to its medicinal value and therapeutic effectiveness. The presence of specific functional small molecules and organic acids such as acetic acid, butyric acid, γ-aminobutyric acid (GABA), salicin, and glycine further amplifies moringa's pharmacological potential. These compounds act as key signaling agents, regulating various physiological and biochemical pathways that support stress tolerance and health-promoting activities. Consequently, developing optimized drying strategies is essential to retain these beneficial bioactive components. RESULTS: This study evaluated the effects of three drying methods-oven drying (50 °C for 24 h), shade drying (120 h), and sun drying (72 h) on the chemical composition and bioactivity of Moringa oleifera leaves. The experiment was designed as a randomized complete block with three replications. Key findings showed that sun and oven drying effectively preserved total phenolic compounds, flavonoids, salicin, and glycine. In contrast, shade drying was more effective at retaining antioxidant activity, as well as acetic acid, butyric acid, and gamma-aminobutyric acid (GABA). Notably, five bioactive compounds-acetic acid, butyric acid, GABA, salicin, and glycine were confirmed and further characterized in the aqueous extract of Moringa oleifera in this study. CONCLUSIONS: Overall, the findings of this study revealed that various drying methods have a significant impact on the preservation of key bioactive compounds in Moringa oleifera. Sun and oven drying were more effective in maintaining phenolic and flavonoid contents, whereas shade drying was better in preserving antioxidant activity and certain organic acids such as acetic and butyric acids. Additionally, specific compounds like salicin and glycine exhibited different responses to drying conditions; salicin reached its highest levels under sun drying, while glycine was maximized with sun drying and moderately retained during oven drying. These results emphasize the importance of selecting appropriate drying techniques based on the targeted bioactive compounds to optimize the medicinal value of herbal plants.