Advance on alkaloids of<italic> Lycium</italic> genus

Natural products derived from medicinal and edible plants, such as polysaccharides, polyphenols, flavonoids, and alkaloids, are a valuable source of potential drug candidates and have attracted interest for their rich structural motifs and diverse physiological activities. Therefore, the discovery of new natural products with unique structures and potential bioactivity from esculent resources has emerged as a promising approach for drug research. In the Solanaceae family, plants of the genus Lycium are relatively abundant, containing about 80 species of plants. Of these, seven species and three varieties are found in China where L. barbarum L., L. chinense Mill., and L. ruthenicum Murr. are most common. Among them, L. barbarum L. and L. ruthenicum Murr are also major medicinal and edible plant resources in Northwest China. “Gou Qi Zi”, also known as Goji or Goji berry, are fruit from L. barbarum L., which has been used as a valuable traditional Chinese herbal medicine and functional food for 2500 years. The earliest recorded mention of these berries is found in the oracle bone script (Jiaguwen) of the Shang Dynasty (1600−1040 BE). Goji berries and Cortex Lycii, which is derived from the root bark of L. chinense and L. barbarum, have many pharmacological functions, such as hypoglycemic, hypolipidemic, immuno-modulatory, antioxidant, anti-aging, neuroprotective, and anti-Alzheimer’s disease properties. Medical and pharmaceutical knowledge regarding L. barbarum has been recorded and summarized in Shennong’s Root and Herbal Classic (Shennong bencao jing) and isolated products are highly desired medicines and contribute to longevity. Li Shizhen also summarized the health and tonic effects of Goji berries in the Compendium of Materia Medica. Many researchers have focused significant attention on the Lycium genus in recent years and various chemical components have been isolated. Phytochemical studies have revealed that the genus Lycium possesses an abundance of secondary metabolites, such as glycerogalactolipids, phenylpropanoids, coumarins, lignans, flavonoids, amides, alkaloids, anthraquinones, organic acids, terpenoids, sterols, steroids and other small molecules and trace elements. Of these, the alkaloids are considered to be one of the main active ingredients. The aim of this review is to focus on identification and biological activity of alkaloids derived from a variety of species in Lycium genus. Up to 2021, at least 124 alkaloids, including 42 amide alkaloids, 31 spermine alkaloids, 17 nortropane alkaloids, 16 pyrrole alkaloids, 4 piperidine alkaloids, 5 imidazole alkaloids, 3 quinoline alkaloids, 3 indole alkaloids, and 3 other alkaloids were reported from different species in the Lycium genus. These can be found in diverse plant structures, such as fruits, root bark, leaves, seeds, or flowers. This review lays a solid foundation for better understanding of pharmacological activities of Lycium-derived compounds and is systematically summarized on the basis of phytochemical studies. This information provides reference values that should facilitate further investigation on additional pharmacological properties and add to the development and utilization of the Lycium.