Quality and production enhancement of fish mint, Houttuynia cordata Thunb., cultivated in a hydroponic planting system with designed plant growth-promoting additives

Fish mint, Houttuynia cordata Thunb. (HCT) is an edible vegetable that has also been used in traditional folk medicines. As both a medicinal herb and a dietary source, HCT has been clinically proven to be a pivotal ingredient in formulas administered to alleviate COVID-19 symptoms. With the increasing market demand for imported materials, ensuring the quality consistency of HCT becomes a significant concern. In this study, the growing time for hydroponically-cultivated HCT with seaweed extract and amino acids added (HCTW) reduced by half compared to conventional soil-cultivated HCT (HCTS). Key quantified components in HCTW, flavonoid glycosides and caffeoylquinic acid derivatives, exhibited a 143% increase over HCTS. These crucial constituents were responsible for possessing antioxidant activity (IC50 < 25 μg/mL) and anti-nitrite oxide production (IC50 < 20 μg/mL). An economically-designed hydroponic system with appropriate additives is proposed to replace HCTS with improvements of growth time, overall production yields, and bioactive qualities.