Assessment of the Anti-inflammatory Effects of Several Native Macrolichens on Carrageenan-Induced Paw Edema in Rats

Background: Inflammation is a natural defense mechanism, but it also plays a role in many chronic diseases such as diabetes, obesity, and cancer. While drugs like indomethacin are commonly used to reduce inflammation, their long-term use can lead to side effects. Lichens, as natural organisms, contain bioactive compounds that may reduce inflammation while minimizing side effects. Objectives: To assess the anti-inflammatory effects of lichen extracts at different doses and compare their efficacy with indomethacin in reducing inflammation in a carrageenan-induced rat model. Methods: A total of 30 male albino Wistar rats, each weighing between 200 - 250 g, were randomly assigned into five groups of six animals. Groups 1 - 3 were administered the test extract at doses of 20, 40, and 80 mg/kg, respectively. Group 4 served as the positive control and received indomethacin at 10 mg/kg, while group 5, the negative control, received an equivalent volume of normal saline (vehicle). All treatments were administered prior to the induction of inflammation. Inflammation was elicited via intraplantar injection of 100 µL of a 1% (w/v) carrageenan solution prepared in 0.9% normal saline. We measured paw volumes using a plethysmometer at baseline (time zero) and again at 1, 2, 3, 4, and 5 hours after the carrageenan injection. Changes in paw volume relative to the baseline were recorded to evaluate the anti-inflammatory effects of the treatments. Results: The study demonstrated that increasing doses of the lichen extract significantly reduced paw swelling, particularly at the 80 mg/kg dosage. However, the lichen extract was not as strong as indomethacin. Still, the natural extract could be a safer option for long-term use because it likely causes fewer side effects than synthetic drugs. Conclusions: Lichen extracts have good potential as a safer alternative to drugs like indomethacin for reducing inflammation. More research is needed to explore higher doses, understand how the extracts work, and improve their formulations to make them more effective.