Sureram S.Chutiwitoonchai N.Pooprasert T.Sangsopha W.Limjiasahapong S.Jariyasopit N.Sirivatanauksorn Y.Khoomrung S.Mahidol C.Ruchirawat S.Kittakoop P.Mahidol University2024-06-182024-06-182024-07-01International Journal of Biological Macromolecules Vol.273 (2024)01418130https://repository.li.mahidol.ac.th/handle/20.500.14594/98862Kratom, Mitragyna speciosa, is one of the most popular herbs in the West and Southeast Asia. A number of previous works have focused on bioactive alkaloids in this plant; however, non-alkaloids have never been investigated for their biological activities. Antiviral and virucidal assays of a methanol leaf extract of Kratom, M. speciosa, revealed that a crude extract displayed virucidal activity against the SARS-CoV-2. Activity-guided isolation of a methanol leaf extract of Kratom led to the identification of B-type procyanidin condensed tannins of (−)-epicatechin as virucidal compounds against SARS-CoV-2. The fraction containing condensed tannins exhibited virucidal activity with an EC50 value of 8.38 μg/mL and a selectivity index (SI) value >23.86. LC-MS/MS analysis and MALDI-TOF MS identified the structure of the virucidal compounds in Kratom as B-type procyanidin condensed tannins, while gel permeation chromatograph (GPC) revealed weight average molecular weight of 238,946 Da for high molecular-weight condensed tannins. In addition to alkaloids, (−)-epicatechin was found as a major component in the leaves of M. speciosa, but it did not have virucidal activity. Macromolecules of (−)-epicatechin, i.e., procyanidin condensed tannins, showed potent virucidal activity against SARS-CoV-2, suggesting that the high molecular weights of these polyphenols are important for virucidal activity.Biochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1016/j.ijbiomac.2024.1330592-s2.0-8519581695618790003