Phytosterols are a kind of natural component including sitosterol, campesterol, avenasterol, ergosterol (Er) and others. Their main natural sources are vegetable oils and their processed products, followed by grains, by-products of cereals and nuts, and small amounts of fruits, vegetables and mushrooms. In this study, three new Er monoester derivatives were obtained from the reflux reaction with Er: organic acids (furoic acid, salicylic acid and 2-naphthoic acid), 1-Ethylethyl-3-(3-dimethyllaminopropyl) carbodiimide hydrochloride (EDCI) and 4-dimethylaminopyridine (DMAP) in dichloromethane. Their chemical structures were defined by IR and NMR. The present study was also undertaken to investigate the antidepressant-like effects of Er and its derivatives in male adult mice models of depression, and their probable involvement of GABAergic and glutamatergic systems by the forced swim test (FST). The results indicated that Er and its derivatives display antidepressant effects. Moreover, one derivative of Er, ergosteryl 2-naphthoate (ErN), exhibited stronger antidepressant activity in vivo compared to Er. Acute administration of ErN (5 mg/kg, i.p.) and a combination of ErN (0.5 mg/kg, i.p.), reboxetine (2.5 mg/kg, i.p.), and tianeptine (15 mg/kg, i.p.) reduced the immobility time in the FST. Pretreatment with bicuculline (a competitive γ-aminobutyric acid (GABA) antagonist, 4 mg/kg, i.p.) and N
-aspartic acid (NMDA, an agonist at the glutamate site, 75 mg/kg, i.p.) effectively reversed the antidepressant-like effect of ErN (5 mg/kg, i.p.). However, prazosin (a α1-adrenoceptor antagonist, 1 mg/kg, i.p.) and haloperidol (a non-selective D2 receptor antagonist, 0.2 mg/kg, i.p.) did not eliminate the reduced immobility time. Altogether, these results indicated that ErN produced antidepressant-like activity, which might be mediated by GABAergic and glutamatergic systems.
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