Immunomodulatory Effect of Plant Extracts and Iridoid Glucosides from Nyctanthes arbortristis Against Systemic Candidiasis in Mice

Abstract

Prophylactic treatment with the ethanol (50%) extracts of the seed and root of the Nyctanthes arbortristis L. (p.o. once daily) provided significant (p < 0.05) protection of Swiss mice against Candida albicans systemic infection. Arbortristoside A and C (iridoid glucosides isolated from seed) at 5 mg/kg (p.o. once daily) enhanced protection. Arbortristoside C was, however, more protective (77.7%) and curative than arbortristoside A based upon increased MST (17 days) and reduced (3-log) CFU of C. albicans from kidney homogenates of treated mice compared to control. The prophylactic (-7 to -1 day) and therapeutic (+1 to +7 days post-infection) regimens (5 mg/kg) of arbortristoside A enhanced protection (71.4%), whereas, arbortristoside C was detrimental to mice. The protective effect of these extracts or fractions may possibly be because of the strong stimulatory activity of arbortristoside A and C elicited by significant (p < 0.001) increase in humoral and delayed type hypersensitivity (DTH) response to sheep red blood cells (SRBC) and macrophage migration index (MMI) in Balb/c mouse. The combined therapy of arbortristoside A or C with ketoconazole (KTZ) did not improve protection of mice. To our knowledge this is the first report of immunomodulatory activity of N. arbortristis against systemic candidiasis in mice.