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The fruit of Hippophae rhamnoides has been widely used for medicinal purposes because of its anti-inflammatory, antioxidant, antiplatelet, and antimicrobial effects. Since there are no clear reports on the therapeutic efficacy of H. rhamnoides in osteoporosis, this study aimed to confirm the potential use of H. rhamnoides for the treatment of osteoporosis through its osteogenic differentiation-promoting effect in ovariectomized mice. Through an in vitro study, we compared the effects of the EtOH extract of H. rhamnoides fruits (EHRF) on the differentiation of C3H10T1/2, a mouse mesenchymal stem cell line, into osteoblasts based on alkaline phosphatase (ALP) staining and the relative expression of osteogenesis-related mRNAs. The EHRF significantly stimulated the differentiation of mesenchymal stem cells into osteoblasts and showed 7.5 times (* p < 0.05) higher osteogenesis than in the untreated control. A solvent fractionation process of EHRF showed that the hexane-soluble fraction (HRH) showed 10.4 times (** p < 0.01) higher osteogenesis than in the untreated control. Among the subfractions derived from the active HRH by preparative HPLC fractionation, HRHF4 showed 7.5 times (* p < 0.05) higher osteogenesis than in the untreated naïve cells, and HRH and HRHF4 fractions showed 22.6 times (*** p < 0.001) stronger osteogenesis activity than in the negative control. Osteoporosis was induced by excision of both ovaries in 9-week-old female ICR mice for in vivo analysis, and two active fractions, HRH and HRHF4, were administered orally for three months. During the oral administration period, body weight was measured weekly, and bone mineral density (BMD) and body fat density were measured simultaneously using a DEXA machine once a month. In particular, during the in vivo study, the average BMD of the ovariectomized group decreased by 0.0009 g/cm2, whereas the average BMD of the HRH intake group increased by 0.0033 g/cm2 (* p < 0.05) and that of the HRHF4 intake group increased by 0.0059 g/cm2 (** p < 0.01). The HRH and HRHF4 intake groups significantly recovered the mRNA and protein expression of osteogenic genes, including ALP, Osteopontin, Runx2, and Osterix, in the osteoporosis mouse tibia. These findings suggest that the active fractions of H. rhamnoides fruit significantly promoted osteoblast differentiation in mesenchymal stem cells and increased osteogenic gene expression, resulting in an improvement in bone mineral density in the osteoporosis mouse model. Taken together, H. rhamnoides fruits are promising candidates for the prevention and treatment of osteoporosis.

Hippophae rhamnoides L. (Elaeagnaceae), commonly known as “Sea buckthorn” and “Vitamin tree”, is a spiny deciduous shrub whose fruit is known for its nutritional composition, such as vitamin C, and is consumed as a dietary supplement worldwide. As part of our ongoing efforts to identify structurally new and bioactive constituents from natural resources, the phytochemical investigation of the extract of H. rhamnoides fruits led to the isolation of one malate derivative (1), five citrate derivatives (2–6), and one quinate derivative (7). The structures of the isolated compounds were elucidated by analysis of 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data and high-resolution electrospray ionization (HR-ESI) liquid chromatography–mass spectrometry (LC/MS) data. Three of the citrate derivatives were identified as new compounds: (S)-1-butyl-5-methyl citrate (3), (S)-1-butyl-1′-methyl citrate (4), and (S)-1-methyl-1′-butyl citrate (6), which turned out to be isolation artifacts. The absolute configurations of the new compounds were established by quantum chemical electronic circular dichroism (ECD) calculation, which is an informative tool for verifying the absolute configuration of organic acid derivatives. The isolated compounds 1–7 were evaluated for their stimulatory effects on osteogenesis. Compounds 1, 3, 4, 6, and 7 stimulated osteogenic differentiation up to 1.4 fold, compared to the negative control. These findings provide experimental evidence that active compounds 1, 3, 4, 6, and 7 induce the osteogenesis of mesenchymal stem cells and activate bone formation.