“Extraction and purification of Proanthocyanidins (PACs) from grape seeds (Vitis vinifera) with in vitro assessment of antimicrobial and antioxidant activity, and in vivo evaluation of 99mTc-PACs complex for tracing bacterial inflammation in mice.”

Proanthocyanidins (PACs) are naturally occurring polyphenolic compounds abundantly present in grape seeds and are widely recognized for their antioxidant and antimicrobial properties. This study aimed to extract, purify, characterize, and evaluate the biological activity of PACs derived from grape seeds, as well as to investigate their potential application as a radiolabeled imaging agent for bacterial inflammation. PACs were extracted and purified, via thin-layer chromatography (TLC). And confirming the presence of functional groups characteristic of condensed tannins using FTIR. The in vitro antimicrobial activity of PACs was evaluated against selected G+ve and G-ve bacterial strains, as well as fungal strains, using disc diffusion method. The results demonstrated strong inhibitory activity against E.coli and S.aureus, while moderate to mild inhibition was observed against other bacterial strains and fungal strains. The total phenolic content (TPC) and total flavan-3-ol content (TFC) were determined using the Folin–Ciocalteu and vanillin assays, yielding values of 435 mg GAE/g and 283 mg CE/g, respectively. Antioxidant activity assessed by the DPPH radical scavenging assay showed a high scavenging capacity of 91.75%. Furthermore, PACs were successfully radiolabeled with technetium-99m (⁹⁹ᵐTc) to form a novel ⁹⁹ᵐTc–PACs complex, achieving an optimized radiochemical yield of 85.6 ± 0.5%. In vivo biodistribution studies in a mouse model of bacterial infection demonstrated preferential accumulation of the radiolabeled complex at sites of inflammation, along with rapid blood clearance and renal excretion. These findings support the potential of ⁹⁹ᵐTc–PACs as a promising radiotracer for non-invasive imaging of bacterial inflammation.