A Review of the Botanical Characteristics, Phytochemistry and Biological Activities of the Fingered Citron Fruit, Citrus medica var. sarcodactylis (Noot.) Swingle

Aims: To bring together the taxonomy, morphology, phytochemistry, molecular pharmacology and toxicology of the fingered citron fruit, Citrus medica var. sarcodactylis (Noot.) Swingle, and to identify the gaps that remain in Vietnamese research. Methodology: The international literature on the species, drawn mainly from Chinese sources and covering both classical pharmacognostic work and recent GC-MS, HPLC-MS/MS and molecular pharmacology studies, was surveyed and organised by part of the fruit, by geographical origin, by class of constituent and by pharmacological target. Results: The constituents show a marked tissue specificity. The exocarp is rich in essential oil (D-limonene 34.69 – 66.9 %), in coumarins and in free flavonoids (hesperidin 370.20 µg/g of dry extract), whereas the mesocarp is rich in limonoids, bound phenolics and polysaccharides. Pharmacologically, the fruit is antitussive and attenuates lung injury by suppressing NF-κB and the NLRP3 inflammasome; it protects the gastric mucosa by modulating HMGB1/TLR4/NF-κB and maintaining PGE2; it lowers blood glucose and blood lipids by activating TGR5/GLP-1, PI3K/AKT/GLUT4 and AMPK/ACC; and it is strongly antimicrobial and antioxidant. No acute toxicity has been recorded, the oral LD50 exceeding 2000 mg/kg. Conclusion: The fingered citron fruit is safe over the range of active doses and possesses a broad spectrum of activity. The data assembled here provide a basis for standardising the herbal material and for developing fingered citron preparations in Vietnam.