Ligustrum japonicum Thunb. Fruits Exert Antiosteoporotic Properties in Bone Marrow-Derived Mesenchymal Stromal Cells via Regulation of Adipocyte and Osteoblast Differentiation

Ligustrum japonicum fruits have been used as a part of traditional medicinal practices and supplements in Korea and Japan. It has been reported to possess various bioactivities, but its antiosteoporotic potential and active substances have not been reported yet. The present study followed an ALP activity and lipid accumulation-guided screening of L. japonicum fruits for antiosteoporotic compounds and isolated salidroside as an active compound. Antiosteoporotic effects of L. japonicum fruits and salidroside were examined in mesenchymal stromal cells by their ability to enhance osteoblast formation by increased ALP activity and osteogenic marker gene expression while suppressing adipogenesis by inhibition of lipid accumulation and adipocyte marker gene expressions. Results showed that salidroside was able to enhance osteoblast differentiation via Wnt/BMP signaling pathway overactivation and suppress the PPARγ-mediated adipocyte differentiation, both through the MAPK pathway. In conclusion, L. japonicum fruits were suggested to possess antiosteoporotic activities and to be a source of antiosteoporotic substances such as salidroside.

A Pentacyclic Triterpene from Ligustrum lucidum Targets γ-Secretase

Amyloid-beta peptides generated by β-secretase- and γ-secretase-mediated successive cleavage of amyloid precursor protein are believed to play a causative role in Alzheimer's disease. Thus, reducing amyloid-beta generation by modulating γ-secretase remains a promising approach for Alzheimer's disease therapeutic development. Here, we screened fruit extracts of Ligustrum lucidum Ait. (Oleaceae) and identified active fractions that increase the C-terminal fragment of amyloid precursor protein and reduce amyloid-beta production in a neuronal cell line. These fractions contain a mixture of two isomeric pentacyclic triterpene natural products, 3-O-cis- or 3-O-trans-p-coumaroyl maslinic acid (OCMA), in different ratios. We further demonstrated that trans-OCMA specifically inhibits γ-secretase and decreases amyloid-beta levels without influencing cleavage of Notch. By using photoactivatable probes targeting the subsites residing in the γ-secretase active site, we demonstrated that trans-OCMA selectively affects the S1 subsite of the active site in this protease. Treatment of Alzheimer's disease transgenic model mice with trans-OCMA or an analogous carbamate derivative of a related pentacyclic triterpene natural product, oleanolic acid, rescued the impairment of synaptic plasticity. This work indicates that the naturally occurring compound trans-OCMA and its analogues could become a promising class of small molecules for Alzheimer's disease treatment.