Evaluation of antipyretic and immunomodulatory activity of aqueous and total crude extract of indigenous red Capsicum annuum L. fruit extracts in albino Wistar rats

Abstract

Background: Capsicum annuum L. is a common plant used as a spice and as a medicinal plant in management of fever and immune booster in local communities though its effectiveness is not fully known. This study aimed at i) determination of the activity of the extracts on the rectal temperature of brewer yeast induced fever in Wistar albino rats (Antipyretic activity), ii) determination of the activity of the total crude extract on the complete blood count (CBC), neutrophil adhesion, phagocytic index and delayed type hypersensitivity (cell mediated immune response) in Wistar albino rats and iii) determination of the activity of the total crude extract on the hemagglutination antibody titers (humoral mediated immune response) in Wistar albino rats. Methods: A laboratory based experimental study where hyperthermia was induced by Brewer’s yeast and different doses of 200mg/kg and 1000mg/kg of aqueous (AQ) and total crude extracts (TCE) were administered. In addition, the immunomodulatory effect of the daily dosing of C. annuum fruits was analyzed using an automated hematological Coulter CBC-5 Hematology Analyzer equipment for a maximum 14 days. Hemagglutination (HA) was analyzed using 96 wells (12x8) flat bottomed titer plate titer. The Hemagglutination (HA) and Delayed-type hypersensitivity (DTH) response model was done for 7 days. Results: 200mg/kg and 1000mg/kg of C. annuum fruit aqueous (AQ) and total crude extracts (TCE) caused a temperature decrease after 0.5 hours after administration. Specifically, at 1000mg/ml there was a temperature decrease of between 4.8-2.2%. The highest decrease in temperature occurred for the C. annuum extract tested at 1000mg/kg. Mean CRP levels decreased in the group that received 1000mg/kg TCE with 75% of the animals showing a reduction after 18 hours of dosing which was similar to the one produced by paracetamol control drug. The overall mean WBC values increased to 0.570 ± 1.39 on day 7. However, there was remarkable decrease to 0.627±1.53 after day 14 and there was statistical difference

in the values between the test group and the normal saline (P<0.05) on day 7, P=0.0317 and on day 14, P=0.0354. The mean % lymphocytes values on D0, D7 and D14 were higher for the 1000mg dose than the control, 2.86±7.01 to 4.35±10.67, 1.26±3.11 to 2.09±5.14, 2.9±7.12, to 3.96±9.70 respectively and there was statistical difference in the values between the test group and the normal saline on day 0 and day 7 (P<0.05), D0 P=0.0098, D7 P=0.0053. The Mean RBC value on day 0 was slightly higher for the control group than the 1000mg dose (0.730±1.79 vs 0.393±0.965) but the reverse was true on day 7 and day 14, there was statistical difference in the values between the test group and the normal saline on day 14 (P>0.05) D14 P=0.0239. No significant changes were observed in the RBC indices and the mean platelets. The mean Hemagglutination titer values for the 1000mg/kg total crude extracts were 5.33±3.08 while that of the positive control (levamisole) and negative control (normal saline) were 4.83±3.31 and 4±2.09 respectively. In addition, results showed that mean paw edema change in length was higher (0.34±0.206) in the group receiving 1000mg/kg bwt following extract administration as compared to the group receiving levamisole (0.28±0.147) and normal saline (0.23±0.052). There was statistical difference in the values between the test group and the normal saline (P<0.05) P=0.032. The mean phagocytic index values for the 1000mg/kg total crude extracts were 0.043±0.018 while of the negative control (normal saline) were 0.024±0.059. No significant changes were noted on phagocytic index and hemagglutination titer values. Conclusion: The findings from this study show that C. annuum aqueous and total crude extracts has antipyretic and immunomodulatory activities with stimulatory effect on the cell - mediated immune response and augmentation of the humoral immune response with the 1000mg/kg bwt TCE showing the highest activity. Findings have provided evidence on the use of the C. annuum fruits in managing of fevers and as immune booster to the local communities and hence its continued use.