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Theoretically, lactic acid bacteria (LABs) could degrade polyphenols into small molecular compounds. In this study, the biotransformation of lotus seedpod and litchi pericarp procyanidins by <i>Lactobacillus plantarum 90</i> (<i>Lp90</i>), <i>Streptococcus thermophilus 81</i> (<i>ST81</i>), <i>Lactobacillus rhamnosus HN001</i> (<i>HN001</i>), and <i>Pediococcus pentosus</i> 06 (<i>PP06</i>) were analysed. The growth curve results indicated that procyanidins did not significantly inhibit the proliferation of LABs. Ultra-high-performance liquid chromatography high-resolution mass spectrometry (UPLC–HRMS) revealed that procyanidin B2 and procyanidin B3 in lotus seedpod decreased by 62.85% and 25.45%, respectively, with <i>ST81</i> metabolised, while kaempferol and syringetin 3-O-glucoside content increased. Although bioconversion did not increase the inhibitory function of procyanidins against glycosylation end-products in vitro, the 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) free radical scavenging capacity and ferric reducing antioxidant power of litchi pericarp procyanidins increased by 157.34% and 6.8%, respectively, after <i>ST81</i> biotransformation. These findings may inspire further studies of biological metabolism of other polyphenols and their effects on biological activity.