Phytochemical Profiling and Antimicrobial Properties of Various Sweet Potato (Ipomoea batatas L.) Leaves Assessed by RP-HPLC-DAD

This study aimed to investigate the leaves of six cultivars of <i>Ipomoea batatas</i> L. from the USA, focusing on their Total Polyphenol Content (TPC), Total Flavonoid Content (TFC), antioxidant, and antimicrobial activities. TPC and TFC ranged from 7.29 ± 0.62 to 10.49 ± 1.04 mg TAE/g Dw, and from 2.30 ± 0.04 to 4.26 ± 0.23 mg QE/g Dw, respectively, with the highest values found in the 'O'Henry' variety. RP-High-Performance Liquid Chromatography identified six phenolic and flavonoid compounds: caffeic acid, chlorogenic acid, 3,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, and quercetin, excluding gallic acid. The highest levels of these compounds were found in acidified methanolic extracts. Antioxidant activities, measured by ABTS and DPPH assays, showed low IC₅₀ values ranging from 94.6 ± 2.76 to 115.17 ± 7.65 µg/mL, and from 88.83 ± 1.94 to 147.6 ± 1.22 µg/mL. Ferric Ion-Reducing Antioxidant Potential (FRAP) measurements indicated significant antioxidant levels, varying from 1.98 ± 0.14 to 2.83 ± 0.07, with the 'O'Henry' variety exhibiting the highest levels. The antimicrobial activity test included five Gram-positive bacteria, three Gram-negative bacteria, and two pathogenic fungi. <i>S. aureus</i>, <i>S. mutans</i>, <i>L. monocytogenes</i>, <i>E. coli</i>, <i>S. dysenteriae</i>, and <i>C. albicans</i> were most susceptible to the methanolic extract. This study underscores the impressive antioxidant and antimicrobial activities of sweet potato leaves, often discarded, making them a valuable source of natural antioxidants, antimicrobials, and other health-promoting compounds.