Proanthocyanidins are natural glycosidase inhibitors with excellent antioxidant activity. This study aims to search for a new source of proanthocyanidins for the prevention and treatment of type 2 diabetes with higher content and better activity and get their structure elucidated. First, the total proanthocyanidins contents (TOPCs), antioxidant activity, antidiabetic activity of seven common Polygonaceae plants were analyzed and compared. Then proanthocyanidins from the rhizome of Fagopyrum dibotrys were purified, and the detailed structure was comprehensively analyzed by ultraviolet visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR), reversed-phase high-performance liquid chromatography-electrospray mass spectrometry (RP-HPLC-ESI-MS), and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The rhizome of F. dibotrys showed the highest TOPCs, the strongest antioxidant, and antidiabetic activities; the TOPCs, antioxidant and antidiabetic activities were all very significantly positively correlated. Proanthocyanidins purified from the rhizome of F. dibotrys showed better antidiabetic activity than grape seed proanthocyanidins (GsPs). Seventy-two proanthocyanidins from trimer to undecamer with a mean degree of polymerization (mDP) of about 5.02 ± 0.21 were identified with catechin and epicatechin as the dominant monomers. Conclusion: Proanthocyanidins are the main antioxidant and antidiabetic active substances of F. dibotrys and are expected to be developed into potential antioxidant and hypoglycemic products.

Andrographis paniculata is an important medicinal herb known as a “natural antibiotic”, which has been used in Southeast Asia for thousands of years. The CONSTANS-like (COL) gene is an important regulatory factor for plant photoperiod flowering and stress response. However, there is currently no detailed research on the COL genes of A. paniculata. In our study, we performed a genome-wide analysis of A. paniculata COL (ApCOL) family members using bioinformatics tools and identified nine ApCOL genes. Based on phylogenetic analysis, ApCOLs were categorized into three groups, with members of the same group having similar structures. Gene duplication events indicated that only one pair of duplicated genes was identified, possibly caused by segmental duplication. In terms of evolutionary relationships, the COL proteins of A. paniculata and Sesamum indicum were closely related, showing that they are highly similar in the phylogenetic tree. In addition, ApCOL genes showed tissue specificity and were specifically highly expressed mainly in leaves and flowers. Based on the cis-regulatory element prediction results, we examined the expression levels of ApCOLs under hormone and salt stress, and ApCOL08 was significantly induced. With subcellular localization results consistent with the prediction, we transformed ApCOL08 into yeast and showed significant resistance to salt stress. Our study suggests that ApCOL genes have important roles in response to abiotic stress and plant development and initially identifies key genes for future molecular regulation studies.