Impact of Various Drying Methods on Bioactive Compounds in Bitter Leaf (Vernonia amygdalina Del.)

Drying is a key method that impacts the preservation of bioactive substances, with different techniques affecting the chemical composition. This study assessed the impact of different drying techniques on the bioactive components of bitter leaf (Vernonia amygdalina Del.). Fresh bitter leaves were cut into small pieces and dried using various methods (CU 40, CU 50, CURK, CUML, PUA, CUA, PUM). Ultrasonic-assisted extraction with 80% methanol at a 1:6 ratio was performed, followed by 30 min of sonication at 200 W and 20 kHz, and evaporation at 65 °C to concentrate the extract. Gas chromatography–mass spectrometry was employed to analyze the compounds present in the extracts. Statistical analyses, including analysis of variance (ANOVA) and correlation analysis, were conducted using Python (statsmodels, scipy, pandas), whereas visualizations such as heatmaps and biplots were generated using seaborn and matplotlib to aid data interpretation. The findings reveal substantial differences in compound retention, with lower drying temperatures such as those used in CU 40 generally resulting in higher retention of bioactive compounds. This indicates that gentler drying methods are more efficacious in preserving certain components, whereas higher drying temperatures tend to degrade them. The distinct relationships between drying methods and compound profiles are further emphasized by correlation analysis, descriptive statistics, ANOVA, hierarchical clustering, and principal component analysis. This underscores the necessity of utilizing specific drying techniques to achieve optimal bioactive compound concentrations. Distinct compound profiles emerged such as 2-formylhistamine and 1,2,6-hexanetriol were prevalent under CU40, benzeneethanamine, and 1,2,3-butanetriol under CU50 and dimethylamine and acetonitrile in CURK. In CUML, butanal, 3-hydroxy- dominated, whereas dl-alanine was the major compound in PUA. PUM demonstrated a significant presence of hydroxylamine (O-decyl-), and CUA featured silane (methyl-) as a prominent component. These insights are key to optimizing extraction and enhancing the therapeutic value of bitter leaf extracts, emphasizing the need for tailored approaches.