The study, “ Aqueous Extract of Phyllanthus niruri Leaves Displays In Vitro Antioxidant Activity and Prevents the Elevation of Oxidative Stress in the Kidney of Streptozotocin-Induced Diabetic Male Rats,” by Nelli Giribabu et al. (2014), investigates Phyllanthus niruri extract and kidney oxidative stress using an experimental diabetes model in male rats.

The researchers evaluated markers of oxidative damage in kidney tissue alongside the activity of key antioxidant enzymes. They also conducted in vitro antioxidant assays and basic phytochemical screening to better understand how the extract interacts with oxidative stress pathways in the diabetic kidney. This summary paraphrases the paper’s methods and findings to provide context for readers without extending the results beyond the original animal data.

The authors describe oxidative stress as a situation where radical-producing systems and radical-scavenging systems are out of balance. In that state, levels of reactive oxygen species (ROS) rise and can damage important macromolecules such as proteins, lipids, carbohydrates, and DNA. They note that chronic high blood sugar, or hyperglycemia, is a major driver of ROS through glucose autooxidation, protein glycation, and the formation of advanced glycation end products (AGE). These processes are linked to diabetic complications that affect the eyes, nerves, and blood vessels.

Within this broader picture, oxidative stress is viewed as a common factor in the development of diabetic nephropathy, a form of kidney disease that can change kidney structure and eventually lead to end-stage renal failure. Phyllanthus niruri, sometimes called “kidney stone crusher,” has a history of traditional use for gastrointestinal and genitourinary problems.

The paper cites previous work showing that this plant can interfere with calcium oxalate crystal formation, reduce urinary stone formation, and has reported anticarcinogenic, hypolipidemic, hepatoprotective, anti-inflammatory, antiplasmodial, and antidiabetic effects.

Earlier research also suggested that P. niruri has antioxidant activity in both animal models and cell or chemical assays. Based on this background, the authors proposed that P. niruri might help prevent oxidative stress in the kidneys of diabetic animals.

The scientific paper combined in vitro and in vivo approaches. First, fresh leaves of Phyllanthus niruri were collected and authenticated. The leaves were air-dried, ground into a powder, and extracted in cold sterile distilled water. The aqueous extract was filtered, concentrated, and then freeze-dried. From 800 grams of leaf powder, the authors obtained about 36 grams of dry extract.

For phytochemical screening, they followed a standard method and tested the extract for several classes of compounds, including alkaloids, flavonoids, saponins, tannins, steroids, lignins, glycosides, terpenoids, polyphenols, coumarins, and resins. To evaluate in vitro antioxidant activity, the extract was tested in DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assays, superoxide radical scavenging assays, hydroxyl radical scavenging assays, and hydrogen peroxide (H₂O₂) scavenging assays. Ascorbic acid was used as a reference compound. For each assay, the authors calculated the percentage of radical inhibition and the IC₅₀ value, which is the concentration needed to inhibit 50 percent of the radicals.

For the in vivo component, adult male Wistar rats were used. Diabetes was induced with a single intraperitoneal injection of streptozotocin (STZ, 55 mg per kg body weight) in citrate buffer. Rats that showed blood glucose levels above 300 milligrams per deciliter and typical signs of diabetes were considered diabetic. The animals were assigned to five groups.

One group was a normal, nondiabetic control. One group consisted of untreated diabetic rats. Two groups of diabetic rats received P. niruri leaf extract at 200 mg per kg or 400 mg per kg. A fifth group of diabetic rats received glibenclamide at 600 micrograms per kg, which served as the standard antidiabetic comparison. All treatments were given orally once a day for 28 days.

After the treatment period, the rats were sacrificed, and the kidneys were collected. Cytosolic fractions from kidney tissue were prepared using a series of centrifugation steps. In these samples, the authors measured lipid peroxidation (LPO) by quantifying malondialdehyde (MDA), and they assessed the activities of three key antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx).

Established spectrophotometric methods were used for each enzyme assay. For statistical analysis, they used analysis of variance and Student t tests, with a P value less than 0.05 considered significant. They also report that post hoc power analysis and tests of normality supported both sample size and data distribution.

Phytochemical screening showed that the aqueous leaf extract of Phyllanthus niruri contained alkaloids, flavonoids, saponins, tannins, lignins, terpenoids, polyphenols, and coumarins. Steroids, glycosides, and resins were not detected in this preparation. The authors point out that several of the detected classes, such as flavonoids and polyphenols, are often associated with antioxidant effects.

In DPPH radical scavenging assays, the P. niruri leaf extract produced a dose-dependent reduction in DPPH radicals. The reported IC₅₀ for the extract was about 90.86 micrograms per milliliter, compared with 25.31 micrograms per milliliter for ascorbic acid. The authors describe the pattern as a “gradual dose-dependent increase in DPPH inhibition.”

Similar dose-related responses were observed in hydroxyl radical, superoxide radical, and hydrogen peroxide scavenging assays, although the IC₅₀ values for the extract were higher than those for ascorbic acid in each case, which indicates that ascorbic acid was more potent on a per mass basis. Based on these experiments, the authors conclude that the leaf extract has in vitro free radical scavenging activity against several different reactive species.

In the diabetic control group, renal MDA levels were markedly higher than in normal rats, with an increase of about 144 percent, which the authors use as an indicator of increased lipid peroxidation. When diabetic rats were treated with P. niruri extract at 200 mg per kg, kidney MDA levels fell by about 28.9 percent compared with untreated diabetic rats.

At the higher dose of 400 mg per kg, MDA levels decreased by about 46.2 percent compared with diabetic controls. In the glibenclamide group, MDA levels were about 39.35 percent lower than in untreated diabetic rats. The authors note that the 400 mg per kg dose of P. niruri was slightly less potent than glibenclamide in limiting the rise in LPO products, but still produced a clear reduction in kidney MDA.

They state that these results “provide evidence that consumption of this extract could prevent elevation of oxidative stress in the kidney in diabetes,” based on the reduced accumulation of lipid peroxidation products.

In kidneys from untreated diabetic rats, superoxide dismutase (SOD) activity was about 50.6 percent lower than in normal rat kidneys. Treatment with 200 mg per kg of P. niruri raised SOD activity by about 43 percent compared with diabetic controls, and treatment with 400 mg per kg raised SOD activity by about 79.9 percent. In the glibenclamide group, SOD increased by about 84.9 percent versus diabetic controls.

Catalase (CAT) activity followed a similar pattern. In diabetic kidneys, CAT activity was about 57.35 percent lower than in normal kidneys. After 28 days of treatment, CAT activity in the 200 mg per kg P. niruri group was about 82.75 percent higher than in untreated diabetic rats, and in the 400 mg per kg group it was about 100 percent higher. Glibenclamide treatment increased CAT by about 96.55 percent compared with diabetic controls. The authors report no significant difference in CAT activity between the 400 mg per kg P. niruri group and the glibenclamide group.

Glutathione peroxidase (GPx) activity was about 29.1 percent lower in diabetic rats than in normal rats. In diabetic rats treated with 200 mg per kg and 400 mg per kg of P. niruri extract, GPx activity rose by about 18.9 percent and 35.8 percent, respectively, compared with untreated diabetic rats. In glibenclamide-treated rats, GPx was about 32.6 percent higher than in diabetic controls. The authors state that the plant extract “prevented deterioration” of GPx activity in kidneys from diabetic rats.

The paper reports strong negative correlations between kidney MDA levels and the activities of SOD, CAT, and GPx. For MDA versus SOD, the correlation coefficient was −0.9675. For MDA versus CAT, it was −0.9856. For MDA versus GPx, it was −0.9872. All correlations were statistically significant.

The authors interpret these findings as showing that “the extent of tissue damage due to oxidative stress was directly related to the levels of endogenous antioxidant enzymes,” meaning that lower enzyme activity was associated with higher lipid peroxidation.

In their discussion, the authors place these findings within what is already known about diabetes and ROS. They point out that hyperglycemia can increase oxidative stress through several pathways, including glucose autooxidation, nonenzymatic protein glycosylation, and activation of the polyol pathway.

Diabetic animals in experimental models often show elevated levels of lipid peroxidation products and weakened antioxidant defense systems, which together contribute to structural and functional damage in the kidney.

The results from this study suggest that aqueous leaf extract of Phyllanthus niruri can both scavenge free radicals in vitro and help maintain endogenous antioxidant enzymes in vivo in the kidneys of STZ induced diabetic rats. The authors state that “this herb protects this tissue against oxidative damage by preventing enzyme dysfunction,” and they note that the decrease in lipid peroxidation seen with treatment may reflect lower levels of free radicals, which is consistent with their in vitro data.

They conclude that their findings support traditional claims that P. niruri is useful in kidney problems related to diabetes, specifically in the context of oxidative stress, within the conditions tested in this animal model.

Taken together, this scientific paper reports that aqueous Phyllanthus niruri leaf extract shows antioxidant activity in both test tube assays and in the kidneys of rats with streptozotocin-induced diabetes.

In these rats, 28 days of oral treatment reduced kidney lipid peroxidation and helped restore SOD, CAT, and GPx activities toward values closer to those seen in normal animals, with some outcomes approaching those of glibenclamide treatment. Because kidney MDA levels were strongly and negatively correlated with antioxidant enzyme activities, the authors suggest that preserving SOD, CAT, and GPx activity is closely tied to limiting oxidative damage in diabetic kidneys.

Within the limits of this model, the study provides experimental support for the idea that P. niruri leaf extract can help prevent oxidative stress in the diabetic kidney.