Phytogenic Immunostimulants: Evaluation of Antifungal and Immunomodulatory Effect of Basil and Lemongrass Extracts in Labeo rohita

High Resolution Image Download MS PowerPoint Slide This study aimed to evaluate the antifungal, antioxidant, and immunomodulatory potential of basil ( Ocimum basilicum ) and lemongrass ( Cymbopogon citratus ) extracts in Labeo rohita fingerlings, with a focus on their efficacy against Aphanomyces invadans COF_AHE F (02). The extracts were analyzed by using liquid chromatography–mass spectrometry (LC-MS), revealing a rich presence of phenolic and flavonoid compounds. Phytochemical and antioxidant assays demonstrated high antioxidant activity, with basil extract (BE) exhibiting higher phenolic, flavonoid, hydrogen peroxide (H 2 O 2 ) scavenging, and saponin content, while lemongrass extract (LGE) showed superior 2,2-diphenyl-1-picrylhydrazyl (DPPH) and dimethyl sulfoxide (DMSO) radical scavenging activity. Agar well diffusion assay confirmed significant antifungal activity with LGE exhibiting superior efficacy. Minimum inhibitory concentration (MIC) analysis showed that both extracts at 500 mg L –1 effectively inhibited A. invadans COF_AHE F (02) spores. The in vivo study demonstrated that fish fed with extract-incorporated diets (1g/kg) exhibited significant ( p < 0.05) improvements in hematological, biochemical, and immunological parameters. There was a notable increase in red blood cell (RBC) and white blood cell (WBC) counts, while alanine aminotransaminase (ALT) and alkaline phosphatase (ALP) levels decreased. Immunological markers, including serum protein, lysozyme, and nitroblue tetrazolium (NBT) activity, were significantly enhanced. Additionally, immune-regulatory genes, such as tumor necrosis factor-α ( TNF-α ), interleukin-1 β ( IL-1β ), and complement component 3 ( C3 ), were upregulated in treated groups. These findings suggest that basil and lemongrass extracts are promising natural immunostimulants for improving fish health and may contribute to disease resistance in aquaculture.