Harvest time and soil-plant relationship effects on phytochemical constituency and biological activities of psidium guajava L. leaves.

Guava (Psidium guajava L.) leaves are deemed promising reservoir of phytoconstituents, with their characteristics potentially influenced by the timing of harvest and the dynamics of soil-plant interactions. The study revealed varying concentrations of minerals and vitamins in guava leaves, predominantly featuring vitamins B and C. Assessment of pigments using HPLC revealed that guava leaves collected in March had higher pigment concentration (461.233 mg/100 g) than that collected in August (447.084 mg/100 g). Quantification of total phenolics in guava leaves collected in March and August resulted in measurements of 435.21 ± 0.17 mgGAE/g and 294.31 ± 0.14 mgGAE/g, respectively. HPLC analysis demonstrated a diverse array of phenolic and flavonoid compounds present in Psidium guajava, with greater abundance and concentration of phenolic and flavonoid compounds in the samples harvested in March compared to those collected in August. For biological evaluation, guava leaves harvested in March demonstrated strong scavenging effect on DPPH and ABTS radicals, and considerable inhibition of carbohydrate-metabolizing enzymes (α-amylase, α-glucosidase, and β-galactosidase) in a dose-dependent manner. Furthermore, the March-collected guava leaves exhibited notable inhibition of COX-2 and 5-LOX enzyme activities, surpassing the effects of leaves collected in August. The study's outcomes demonstrate richness of phytoconstituents in guava leaves, which underpin various biological functions, particularly during spring relative to the summer. This highlights the importance of the timing of collection in assessing phytochemical properties and their biological implications, highlighting the necessity of considering this aspect when sampling guava leaves.