Effect of diet containing the purple coneflower, Echinacea purpurea extract and powder on innate immune-antioxidant factors in the hemolymph of Pacific white shrimp, Litopenaeus vannamei under pH stress

Introduction: One of the novel approaches in stress management and health improvement in aquatic organisms is the use of dietary supplements with immune-boosting properties. Purple coneflower, Echinacea purpurea, as one of the medicinal plants, due to its phenolic compounds, glycosides, alkaloids, and antioxidant, anti-inflammatory, and immune-boosting properties, can be used as a natural supplement to improve immune system performance and resistance against environmental stresses in aquaculture. Research in aquatic species has shown that the use of medicinal plant including E. purpurea can have positive effects on the physiological status, immunity, and health of aquatic organisms when faced with environmental stresses and diseases. In this study, the effects of a diet containing purple coneflower extract and powder on hematological and immune-antioxidant factors of the hemolymph of Pacific white shrimp (Litopenaeus vannamei) under pH stress were investigated.
Materials and Methods: Shrimp were fed with diets containing different concentrations of purple coneflower extract (0.25%, 0.5%, and 1%) and powder (0.25%, 5% and 10%) for 68 days. Subsequently, the performance of blood and immune-antioxidant factors in the hemolymph, including total and differential hemocyte counts and the activity of enzymes such as lysozyme, superoxide dismutase, glutathione peroxidase, and catalase were evaluated after exposure to acidic (pH 4.5) and alkaline (pH 9.5) stress conditions for 24 hours.
Results and Discussion: Under acidic and alkaline pH conditions, the total hemocyte count was significantly lower than in the control group in different treatments except for treatment containing 0.25% extract of purple coneflower (P<0.05). The large granular cells did not show significant difference among treatments in response to acidic pH stress (P>0.05), however, they were significantly lower than the control group in different treatments except for treatment containing 0.25% extract of purple coneflower in response to alkaline pH stress (P<0.05). Additionally, the results showed that under acidic and alkaline pH stress conditions, the semigranular and hyaline cells and the activity of lysozyme, superoxide dismutase, glutathione peroxidase, and catalase, did not show significant differences compared to the control group at lower doses of extract and higher doses of purple coneflower (P>0.05). However, with an increase in extract dosage and a decrease in powder dosage, the immune-antioxidant factors in the shrimp's hemolymph were reduced compared to the control group.
The results of this study indicate that purple coneflower, at certain concentrations, led to changes in the hemolymph immune-antioxidant response under acidic and alkaline pH conditions, resulting in a reduction in hemocyte counts and then activity of immune-antioxidant enzymes. The results showed that the plant, at some doses, was not effective in regulating the immune-antioxidant response of shrimp under acidic and alkaline pH conditions.
Conclusion: The results of this study indicated that different concentrations of purple coneflower extract and powder can affect the immune-antioxidant system of shrimp in response to pH stress. The treatment with 0.25% the purple coneflower extract exhibited the most positive effect on shrimp immunity in response to pH stress, where hemocyte counts and immune-antioxidant enzyme activity in this treatment did not differ significantly from the control group under both acidic and alkaline pH stress. This positive effect is likely due to the presence of active metabolites, especially active polyphenolic compounds and polysaccharides, in the purple coneflower extract. When using the purple coneflower as a natural supplement in shrimp feeding, their concentrations should be carefully managed to prevent negative impacts on the immune system.