Solvent-Dependent Extraction and Regional Bioactivity Variance in Psidium guajava: A Multi-Region Assessment of Antimicrobial Spectrum and Antioxidant Efficacy

Abstract

Background: The therapeutic efficacy of Psidium guajava (L.) Merr. is significantly influenced by the polarity of the extraction solvent and geographic provenance. However, multi-regional comparative studies integrating solvent-dependent phytochemical partitioning with biological activity are limited. This study investigates the influence of three distinct Indian geographic regions and three solvent systems on the phytochemical profile, antimicrobial spectrum, and antioxidant capacity of guava leaf extracts.

Methods: Leaves were collected from Tamil Nadu (TN; tropical lowland), Himachal Pradesh (HP; temperate foothills), and Uttarakhand (UK; sub-Himalayan mid-hills). Sequential extraction was performed using petroleum ether (PE), n-butyl alcohol (NBA), and distilled water (AQ). Qualitative phytochemical screening was conducted. Antimicrobial activity was assessed by the agar well diffusion method against six clinically relevant pathogens. Antioxidant capacity was quantified using DPPH and ABTS radical scavenging assays. GC-MS profiling was performed on an Agilent 7890A/5975C system.

Results: Phytochemical diversity varied significantly, with Uttarakhand extracts exhibiting the highest class diversity (17/18), followed by Tamil Nadu (14/18) and Himachal Pradesh (12/18). The n-butyl alcohol fraction was the most bioactively potent. Antimicrobial testing revealed a regional hierarchy of TN > UK > HP against most pathogens, with Staphylococcus aureus demonstrating the highest susceptibility (ZOI: 20.7 mm for TN-NBA). DPPH and ABTS radical scavenging activity followed a regional hierarchy of TN > HP > UK, with Tamil Nadu achieving the highest radical scavenging capacity (82.2% DPPH, 61.75% ABTS), followed by Himachal Pradesh (79.80% DPPH, 57.45% ABTS) and Uttarakhand (78.5% DPPH, 55.75% ABTS). GC-MS profiling identified three distinct regional chemotypes: flavonoid-glycoside (TN), sesquiterpene-phytosterol (HP), and phenolic acid-coumarin (UK).

Conclusion: Geographic origin and solvent polarity are critical determinants of the bioactive potential of P. guajava leaf extracts. Despite lower phytochemical class diversity, the Tamil Nadu accession demonstrated superior antimicrobial and antioxidant efficacy due to a high concentration of specific potent polyphenols such as EGCG and quercetin glycosides.