Quercetin is a natural flavonoid compound with outstanding antioxidant, anti-inflammatory, antibacterial and immunomodulatory activities, widely used in pharmaceutical raw materials, health food, dietary supplements and cosmetic industry. It can scavenge free radicals in the human body, inhibit lipid peroxidation, delay cell aging and protect cardiovascular system by lowering blood lipid and improving capillary elasticity. In pharmaceutical research, it acts as an important intermediate and raw material for developing anti-tumor, anti-viral, anti-allergy and liver-protecting drugs. It is extensively added into functional health products for regulating immunity, relieving chronic inflammation and assisting sub-health conditioning. In cosmetics, it is used as natural antioxidant and whitening additive to inhibit melanin formation, soothe sensitive skin and improve skin antioxidant capacity. It also serves as analytical reference standard, plant extraction marker and raw material for fine chemical synthesis of flavonoid derivatives.

Quercetin belongs to low-toxic natural plant extract under conventional use dosage, but still has certain irritation risk. Direct skin contact may cause mild dryness, redness and slight allergic reaction for sensitive skin groups; long-term skin contact should be avoided. Eye splash will cause stinging, foreign body sensation and conjunctival hyperemia, need immediate washing with plenty of running clean water. Inhalation of fine powder may irritate respiratory mucosa, resulting in throat dryness and mild cough discomfort. Excessive oral intake in a short time may cause gastrointestinal symptoms such as nausea, bloating and diarrhea. During weighing and handling, operators should wear dust-proof mask, chemical resistant gloves and protective goggles, keep working area well ventilated and avoid dust floating. Store in sealed, dry, cool and dark environment, strictly protected from light and high temperature to prevent oxidation and deterioration, keep away from strong oxidants and strong alkali substances. Waste materials and contaminated packaging shall be disposed of according to biochemical waste regulations, and arbitrary discharge into water and soil is forbidden to avoid potential ecological cumulative impact.