Fuente: WIPO "tomato" A polyphenol-rich composition is orally administered to alleviate a sign or symptom of a post-viral syndrome, and preferably post-COVID syndrome. Most typically, the composition comprises at least 50 wt % total catechins, at least 20 wt % total chlorogenic acids, and optionally up to 30 wt % total supplemental antioxidants. The composition may be formulated from a green coffee bean extract, a green tea extract, a turmeric extract, a tart cherry or extract thereof, a broccoli or extract thereof, and a kale or extract thereof. Notably, such compositions were effective in individuals post SARS-CoV2 infection to reduce proinflammatory cytokines and interleukins, increase NOHb, and to reduce reactive oxygen species due to mitochondrial dysfunction, iNOS activity, and NOX2 activity.