Abstract
Harpagophytum procumbens (Burch.) DC. ex Meisn. is a traditional remedy for osteoarticular diseases, including osteoarthritis (OA), although the bioactive constituents and mechanisms involved are yet to be clarified. In the present study, an aqueous H. procumbens root extract (HPE; containing 1.2% harpagoside) was characterized for its effects on synoviocytes from OA patients and phytochemical composition in polyphenols, and volatile compounds were detected. HPE powder was dissolved in different solvents, including deionized water (HPEH2O), DMSO (HPEDMSO), 100% v/v ethanol (HPEEtOH100), and 50% v/v ethanol (HPEEtOH50). The highest polyphenol levels were found in HPEDMSO and HPEEtOH50, whereas different volatile compounds, mainly β-caryophyllene and eugenol, were detected in all the extracts except for HPEH2O. HPEH2O and HPEDMSO were able to enhance CB2 receptor expression and to downregulate PI-PLC β2 in synovial membranes; moreover, all the extracts inhibited FAAH activity. The present results highlight for the first time a multitarget modulation of the endocannabinoid system by HPE, likely ascribable to its hydrosoluble compounds, along with the presence of volatile compounds in H. procumbens root. Although hydrosoluble compounds seem to be mainly responsible for endocannabinoid modulation by HPE, a possible contribution of volatile compounds can be suggested, strengthening the hypothesis that the entire phytocomplex can contribute to the H. procumbens healing properties.
Highlights
Osteoarthritis (OA) is a pathology of the whole joint structure, involving several cellular and molecular processes, in different types of cells, such as chondrocytes, osteoblasts, synoviocytes, and Nutrients 2020, 12, 2545; doi:10.3390/nu12092545 www.mdpi.com/journal/nutrientsNutrients 2020, 12, 2545 immune cells [1]
Tannins were mainly recovered by H2 O and dimethyl sulfoxide (DMSO), their amount in HPEH2O and HPEDMSO being 1.5- to 1.9-fold higher than that found in HPEEtOH100 and
The highest extraction power was exhibited by DMSO; HPEDMSO exhibited about 1.5- to 3-fold and 1.5- to 1.7-fold higher concentrations of total flavonoids and flavonols than HPEEtOH50 or HPEEtOH100 and HPEH2O, respectively (Table 2)
Summary
Osteoarthritis (OA) is a pathology of the whole joint structure, involving several cellular and molecular processes, in different types of cells, such as chondrocytes, osteoblasts, synoviocytes, and Nutrients 2020, 12, 2545; doi:10.3390/nu12092545 www.mdpi.com/journal/nutrientsNutrients 2020, 12, 2545 immune cells [1]. Osteoarthritis (OA) is a pathology of the whole joint structure, involving several cellular and molecular processes, in different types of cells, such as chondrocytes, osteoblasts, synoviocytes, and Nutrients 2020, 12, 2545; doi:10.3390/nu12092545 www.mdpi.com/journal/nutrients. An association between inflammation and endocannabinoid receptors has been described [3]. The role of CB2 receptors seems very interesting in OA inflammation. CB2 is a peripheral cannabinoid receptor and has been found in immune system cells, raising the possibility that the endocannabinoid system could have a role in immunomodulatory processes [3]. In this respect, several studies reported that mice lacking CB2 receptors showed an exacerbated inflammatory phenotype [4]. CB2 receptors are involved in inhibiting nociceptive transmission [5]
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