Comprehensive Analysis of Conventional and Bioactive Compositions of the Exocarp of Five Mainly-Planted Ginkgo Biloba Varieties

Ginkgo biloba (G. biloba) exocarp, a by-product of seed production, is produced in an amount of over 75,000 tons annually in China. However, due to the lack of suitable processing methods, it is predominantly discarded as agricultural waste, resulting in substantial waste of resource. To seek new development directions, this study first comprehensively evaluated the conventional and bioactive compositions of the exocarps of the five mainly-planted G. biloba varieties. The results indicated that G. biloba exocarps contained some preponderant bioactive compositions, including ginkgolic acids (GAs, 54.10~85.42 mg/g), proanthocyanidins (26.62~52.96 mg/g), and polysaccharides (29.72~51.72 mg/g). G. biloba exocarps were also abundant in terpene trilactones (TTLs, 332.63~780.31 μg/g), flavonoids (70.88~109.26 μg/g), and 6-hydroxykynurenic acid (6-HKA, 43.19~302.99 μg/g). The conventional components of G. biloba exocarps were mainly ash, crude fiber, and fat. The contents of starch and protein were lower; thus, G. biloba exocarp exhibits a lower nutritional value. G. biloba exocarps have the potential to be the best resource for the preparation of GAs, proanthocyanidins, and polysaccharides. This study provides a theoretical basis for the development and utilization of G. biloba exocarps.