1Department of Pharmacology, Srinivas College of Pharmacy, Valachil, Mangalore, Karnataka, India. 574143.
2Principal and Director, Srinivas College of Pharmacy, Valachil, Mangalore, Karnataka, India. 574143.
Background and Objective: Pain significantly impacts global health, and conventional medications often have serious side effects, prompting the exploration of safer alternatives from natural sources. This study aimed to evaluate the analgesic activity of ethanolic extracts from Macaranga peltata leaves, traditionally used for pain management in parts of Asia. Methodology: Macaranga peltata leaves were collected, authenticated, and extracted using ethanol. Phytochemical screening was conducted, and analgesic activity was assessed using Eddy's Hot Plate method in Swiss albino mice. Four groups were tested: control (vehicle), standard (Tramadol 5 mg/kg), and two test groups receiving 200 mg/kg and 400 mg/kg of the extract, respectively. Results: The extract yielded 3.5% and contained alkaloids, flavonoids, phenolic compounds, tannins, and saponins. It showed dose-dependent analgesic effects, with the 400 mg/kg dose significantly increasing pain latency (p<0.01) at 30, 60, and 90 minutes, while the 200 mg/kg dose showed mild, non-significant increases. Tramadol exhibited the strongest analgesic effect (p<0.001). At 90 minutes, maximum pain inhibition was: Tramadol (49.08%), Extract 400 mg/kg (37.15%), Extract 200 mg/kg (25.46%). Conclusion: The ethanolic extract of Macaranga peltata leaves demonstrated significant dose-dependent analgesic activity, supporting its traditional use. While not as potent as Tramadol, the extract, particularly at 400 mg/kg, shows promise as a natural analgesic alternative, warranting further research into its mechanisms of action, safety profile, and potential clinical applications.
Pain is a complex global health issue that significantly impacts the quality of life for millions of individuals. It is a defensive response triggered by harmful stimuli and is characterized as an unpleasant sensory and emotional experience associated with actual or potential tissue damage (1). While conventional pain medications like non-opioid analgesics, NSAIDs, and opioids are widely used, they are often associated with serious side effects, such as gastrointestinal ulcers, renal dysfunction, cardiovascular risks, and addiction potential (2). Chronic pain, affecting up to 50% of adults globally, underscores the urgent need for safer and more effective alternatives. This growing concern has prompted a shift towards exploring natural sources, particularly medicinal plants, which have been used for centuries in traditional medicine for their potential analgesic properties and reduced side effects (3,4). Macaranga peltata, a plant native to parts of Asia, including the Western Ghats of India, is one such species that holds promise for natural pain management (5,6). Traditionally used for treating ailments like pain, inflammation, fever, and skin diseases, M. peltata contains bioactive compounds such as flavonoids, tannins, and terpenoids, which have shown analgesic and anti-inflammatory properties in various plant species (6,7). However, despite its extensive use in folk medicine, there is a lack of robust scientific evidence supporting the pain-relieving effects of M. peltata, particularly its leaves. This gap in the literature presents a valuable opportunity to investigate the analgesic potential of this plant and validate its traditional uses through modern scientific methods. The present study aims to evaluate the analgesic activity of ethanolic extracts from Macaranga peltata leaves using Eddy’s Hot Plate test, an established experimental model in mice to assess centrally mediated pain. By addressing this knowledge gap, this research will provide insights into the analgesic properties of M. peltata, potentially leading to the development of safer, plant-based pain management therapies. Such findings could significantly contribute to the scientific validation of traditional medicinal uses and the broader pursuit of alternative, natural pain relief solutions in modern healthcare.
METHODOLOGY
The leaves of Macaranga peltata were collected from local areas of Puttur, Karnataka, in July 2024. The plant material was authenticated by Dr. Siddaraju M. N., Assistant Professor and Research Guide, Dept of Botany, University College Mangalore, on 16/07/2024. The leaves were thoroughly washed with water to remove dust and air-dried at room temperature in the shade for approximately two weeks until moisture-free. The dried leaves were then powdered using a mechanical grinder and stored in an airtight container to maintain their integrity.
The powdered Macaranga peltata leaves were subjected to maceration with ethanol (99.5%) in a ratio of 1:4. The mixture was left inside a sealed 1000 ml conical flask for 48 hours at room temperature. After the extraction process, the solution was first filtered using a muslin cloth and then through filter paper. The filtrate was concentrated using a water bath and then dried in a vacuum oven. The crude ethanolic extract was preserved in a refrigerator for further use (8).
The ethanolic extract of Macaranga peltata leaves was subjected to preliminary phytochemical screening to detect the presence of various bioactive compounds, including alkaloids, flavonoids, tannins, terpenoids, steroids, glycosides, and phenolic compounds. These phytochemicals are important for assessing the therapeutic potential of the plant (9).
d. Preparation of Stock Solution of Extract for Dosing:
The ethanolic extract of Macaranga peltata was weighed and suspended in distilled water for dosing. The suspension was sonicated to ensure complete dissolution. Fresh preparations of the extract were made before each administration. The doses selected for the study were 200 mg/kg and 400 mg/kg, based on a previous study on Macaranga peltata leaves. The extract was administered orally using an oral gavage.
Healthy Swiss albino mice weighing 35-40 grams of either sex were procured from the Animal House of Srinivas College of Pharmacy, Mangalore. The animals were housed in sanitized polypropylene cages with sterile paddy husk as bedding. They were maintained under standard conditions, including a temperature of 22±2°C, relative humidity of 50±5%, and a 12-hour light/dark cycle. The mice had free access to a standard palette diet and water. The animals were acclimatized for at least one week before the experiments. Food access was restricted 3 hours before dosing (10).
The Institutional Animal Ethics Committee (IAEC) of Srinivas College of Pharmacy approved the experimental protocol (Approval No. SCP/IAEC/JUL/2024-234). All procedures were carried out in strict adherence to the ethical guidelines outlined by the Committee for the Control and Supervision of Experiments on Animals (CCSEA), under the Ministry of Animal Welfare Division, Government of India, to ensure humane care and use of laboratory animals.
Eddy’s Hot Plate Method
The Eddy's Hot Plate test was employed to assess the central analgesic activity of the extract. The apparatus consists of a heated metal plate maintained at a temperature of 55±0.5°C. A Plexiglas cylinder with a height of 26 cm and a diameter of 19 cm was used to prevent the animals from escaping. Swiss albino mice were divided into four groups, each comprising six animals, as follows:
The hot plate latency period, i.e., the time taken by the mice to respond by licking their paws or jumping, was measured at 0, 30, 60, and 90 minutes after drug administration. A cut-off time of 15 seconds was set to prevent tissue damage, and any mouse that did not respond within this time was immediately removed from the plate (11).
Statistical Analysis:
The results of the analgesic activity were expressed as Mean ± SEM. Statistical comparisons between groups were made using one-way Analysis of Variance (ANOVA), followed by Dunnett’s multiple comparison test to evaluate the significance of the differences between the control, standard, and test groups. P - value of ? 0.05 was considered statistically significant. The analysis was conducted using GraphPad Prism software.
Fig. 1. Schematic Representation of the Extraction, Phytochemical Screening, and Analgesic Evaluation of Macaranga peltata Leaves.
RESULT
Extraction of Plant Material
The extraction of Macaranga peltata leaves yielded a dark green, semi-solid crude extract with a percentage yield of 3.5%.
Preliminary Phytochemical Screening
The preliminary phytochemical screening of the ethanolic extract of Macaranga peltata revealed the presence of several bioactive compounds, which are shown in Table 1. These compounds include carbohydrates, alkaloids, flavonoids, phenolic compounds, tannins, saponins, anthraquinone glycosides, and steroids. Proteins and amino acids were not detected.
Table 1: Results of Preliminary phytochemical investigation of ethanolic screening of ethanolic extract of Macaranga peltata leaf.
Analgesic Activity of the ethanolic extract of Macaranga peltata
In the present study, the analgesic activity of the ethanolic extract of Macaranga peltata was evaluated using the Eddy’s Hot Plate method.
Table 2: Effect of Ethanolic extract of Macaranga peltata leaves in mice using Eddy’s hot plate method
Fig.2. Effect of Ethanolic extract of Macaranga peltata leaves in mice using Eddy’s hot plate method
Table 2 and Figure 2 illustrate a dose-dependent analgesic effect of the ethanolic extract of Macaranga peltata leaf (EEMPL) in comparison to the standard drug Tramadol, as assessed using Eddy’s hot plate method. The control group (vehicle) showed no significant changes in latency times, indicating no analgesic activity. However, the group treated with Tramadol (5 mg/kg) exhibited a significant increase in latency at 30, 60, and 90 minutes, reaching a maximum of 7.415 seconds at 90 minutes. The percentage inhibition of pain response for this group was 49.08% at 90 minutes, demonstrating strong analgesic activity (p<0>
These findings suggest a dose-dependent response, where the higher dose of EEMPL (400 mg/kg) produced a significantly greater analgesic effect than the lower dose, though neither dose matched the efficacy of Tramadol. This dose-dependent increase in latency times indicates that Macaranga peltata exhibits greater analgesic potential at higher concentrations, supporting its possible use as a natural analgesic agent.
DISCUSSION
Pain, or algesia, is a vital protective response to harmful stimuli, typically managed with a variety of medications. Analgesics can be classified into non-opioid analgesics (e.g., NSAIDs), opioid analgesics, and corticosteroids (12). Non-opioid analgesics, such as NSAIDs, are commonly used for mild to moderate pain and function by inhibiting prostaglandin synthesis, reducing inflammation and pain (13). However, long-term use of NSAIDs can lead to side effects like gastrointestinal issues, kidney damage, and cardiovascular risks (14). Opioid analgesics, such as Tramadol and morphine, are more potent and prescribed for moderate to severe pain. These medications work by interacting with opioid receptors in the central nervous system (CNS) to reduce pain perception, but they come with serious side effects like dizziness, nausea, constipation, and the risk of addiction and dependence (15). Corticosteroids are also used in specific inflammatory conditions, but prolonged use can lead to adverse effects such as immune suppression and weight gain (16). Due to the potential side effects associated with synthetic drugs, the interest in herbal medicines as analgesics has grown significantly (17). Natural compounds found in plants often exhibit fewer side effects and can offer therapeutic benefits, including pain relief (18). Several herbs, such as turmeric, ginger, and willow bark, have been traditionally used for their anti-inflammatory and analgesic properties (19). In recent years, scientific studies have begun validating the efficacy of these herbal remedies, revealing that bioactive compounds like flavonoids, alkaloids, and saponins play a role in modulating pain and inflammation (20). In the present study, Tramadol was used as a reference standard to compare the analgesic effects of the ethanolic leaf extract of Macaranga peltata. Tramadol, a well-known opioid analgesic, acts through a dual mechanism: binding to ?-opioid receptors in the CNS to inhibit pain transmission and inhibiting the reuptake of serotonin and norepinephrine, which further modulates pain perception and mood. This dual action makes Tramadol highly effective for a range of pain conditions, though it carries risks like dependence, tolerance, and side effects, particularly with long-term use (21). Using Eddy’s hot plate method, the analgesic effect of Macaranga peltata was evaluated in comparison to Tramadol. As expected, Tramadol (5 mg/kg) significantly increased the latency time in response to heat-induced pain at 30, 60, and 90 minutes, reflecting potent analgesic activity (P<0>
FUTURE DIRECTIONS
The findings concerning the analgesic potential of Macaranga peltata suggest several avenues for future research, focusing on isolating and identifying the specific bioactive compounds in the ethanolic extract using advanced techniques such as chromatography and mass spectrometry to elucidate their pharmacological properties. Investigating the mechanisms underlying the analgesic effects is essential; future studies could explore how these compounds interact with specific receptors, including COX enzymes and opioid receptors, clarifying the pathways involved in modulating pain response and inflammation. While the current study utilized Eddy’s hot plate method, additional in vivo studies employing various pain models, such as chemical-induced and inflammatory pain, would provide a more comprehensive understanding of the analgesic effects. In vitro studies should also evaluate the anti-inflammatory properties of the extracts and their active constituents. Furthermore, assessing the safety profile and potential toxicity of Macaranga peltata is crucial for its consideration as a therapeutic agent, necessitating both acute and chronic toxicity studies to establish a safe dosage range and identify any potential side effects. Should preclinical studies validate the efficacy and safety of Macaranga peltata, the next step would involve conducting clinical trials to assess its analgesic properties in humans, comparing its effectiveness and safety to conventional analgesics such as Tramadol and NSAIDs. Research could also investigate the development of various formulations, such as tablets, capsules, and topical applications, for pain management, evaluating the bioavailability and stability of the active compounds. Additionally, exploring the potential synergistic effects of Macaranga peltata in conjunction with other analgesics, both opioid and non-opioid, may yield a more effective pain management strategy with reduced side effects. Beyond its analgesic properties, the anti-inflammatory, antioxidant, and neuroprotective effects of Macaranga peltata warrant further examination to enhance its utility in various clinical contexts. By pursuing these future research directions, a clearer understanding of the analgesic properties of Macaranga peltata may be established, positioning it as a valuable natural alternative in pain management strategies.
CONCLUSION
This study provides compelling evidence for the analgesic potential of Macaranga peltata leaves, demonstrated through a dose-dependent increase in pain latency using the Eddy's Hot Plate method. The ethanolic extract, particularly at a dose of 400 mg/kg, exhibited significant analgesic effects, although these effects were not as potent as the standard analgesic Tramadol. Phytochemical screening confirmed the presence of various bioactive compounds known for their analgesic and anti-inflammatory properties, supporting the traditional medicinal uses of the plant. The findings highlight the potential of Macaranga peltata as a natural alternative for pain management, encouraging further research into its mechanisms of action, safety profile, and potential applications in clinical settings.
REFERENCE
Ramdas Bhat, Vaishnavi, Kavana D K., Megha M., Rithin K., Sinchana S Bhat, A. R. Shabaraya , Evaluation Of Analgesic Activity Of Macaranga Peltata Leaf Extract On Experimental Animals, Int. J. of Pharm. Sci., 2024, Vol 2, Issue 10, 1454-1462. https://doi.org/10.5281/zenodo.13996260
10.5281/zenodo.13996260
