Chaenomeles Lindl. Rosaceae. X superba (Frahm)Rehder. Japanese quince, flowering quince. 'Issai White'. A garden hybrid C. speciosa x C. japonica. This white-flowered cultivar's name, 'Issai', means 'early flowering' in Japanese.

Oakeley, Dr. Henry F. (2013). Wellcome Library notes. Link

The related species Chaenomeles sinensis is medicinal

http://www.pfaf.org https://pfaf.org/user/Plant.aspx?LatinName=Chaenomeles+sinensis

Chaenomeles Lindl. Rosaceae. X superba (Frahm)Rehder. Japanese quince, flowering quince. 'Issai White'. A garden hybrid C. speciosa x C. japonica. This white-flowered cultivar's name, 'Issai', means 'early flowering' in Japanese. Distribution: Parents of Japanese origin, garden cultivar. Fruit is rich in vitamin C, contains mucilage used as a demulcent. Gang Zhao et al (Science Direct 90(3):363-371 (2008)) report experimental antiparkinsonian potential. Used in compound medicines for neuralgia, migraine and depression in Traditional Chinese Medicine. Seeds reputed to contain cyanogenic glycosides.

Oakeley, Dr. Henry F. (2013). Wellcome Library notes. Link