Study of the Antioxidant and Immunomodulatory Activity of the Total Aqueous Extract of Clerodendrum splendens (G.Don) Leaves (Lamiaceae)

Abstract

Clerodendrum splendens (Lamiaceae) is a plant with therapeutic properties, traditionally used in several countries for the treatment of several diseases. The objective of this study was to evaluate the antioxidant and immunomodulatory activity of the total aqueous extract obtained from the leaves of C. splendens in order to contribute to a better knowledge of the therapeutic effects of this plant. It consisted in the realization of the antioxidant activity of ETAC according to the following methods: the DPPH test and the iron reducing power test (FRAP).    For the DPPH test, 50 µl of each of the different concentrations of the extract were incubated with 5 ml of a 0.004% methanolic solution of DPPH. After an incubation period of 30 minutes, the absorbances at 517 nm were recorded. The 50% inhibitory concentration of DPPH activity (IC50) expressed in µg/ml of each extract was calculated and compared with that of butylated hydroxytoluene (BHT) taken as the reference antioxidant. The Ferric Reducing/Antioxidant Power (FRAP) assay measures the reducing power of antioxidants in a mixture by their ability to reduce ferric tripyridyl-triazine (Fe3+ -TPTZ) to ferrous (Fe 2+-TPTZ) at acidic pH. 900 µl of the FRAP reagent, previously incubated at 37°C, was mixed with 70 µl of doubly distilled water and 30 µl of the sample (with appropriate dilutions). The increase in absorbance at 593 nm was then monitored for 30 minutes at 37 °C. A range of FeSO4.7H2O, a reducing standard, between 0 and 2000 µM was used to calculate the FRAP values of the extracts and the standard antioxidant (BHT). The results of the study showed that ETAC has a good free radical scavenging activity compared to the activity of BHT, which is a synthetic antioxidant used as a standard. Thirty-two (32) rats weighing between 150 and 200 grams on average were used for the immunomodulatory effect of ETAC. The rats were randomly divided into four (4) batches of eight (8) rats each according to their weight. Each batch consisted of four (4) male and four (4) female animals distributed in different bins according to sex. The control rats were each given 1 ml of distilled water daily by gavage for the 28-day treatment period. The three (3) test batches (batches 1; 2 and 3) received 125 mg/kg bw; 250 mg/kg bw and 500 mg/kg bw of ETAC by gavage daily for 28 days. ETAC significantly increased white blood cell and lymphocyte counts at 125 and 250 mg/kg bw. The increase was greatest at 250 mg/kg bw. Only at 250 mg/kg bw was there a significant increase in neutrophils. Histological sections showed no structural or functional abnormalities in the thymus and spleen.