Unripe mature pawpaw seeds may provide a cheap and accessible treatment for kidney damage and sickle cell anaemia. CHUKWUMA MUANYA writes.

MORE Nigerians are coming down with chronic kidney disease. The cost of managing the disease, with regular dialysis, and the search for kidney donors have rendered most affected families bankrupt.

But Nigerian researchers claimed that seed extracts of unripe mature fruits of pawpaw (Carica papaya) can protect the kidneys from damage and could offer hope for the treatment of poison-related kidney (renal) diseases.

The study titled “Nephroprotective activities of the aqueous seed extract of

Carica papaya in carbon tetrachloride induced renal injured Wistar rats: A dose- and time-dependent study,” was published in Biology and Medicine.

Nephro-protective means kidney-protecting. Carbon tetrachloride (CCl4) is an environmental toxicant. CCl4 initiates lipid peroxidation, disrupts membrane integrity and causes cell death. It is implicated in kidney damage.

Lipid peroxidation is a well-defined mechanism of cellular damage in both animals and plants that occurs in vivo during ageing and in certain disease states.

The researchers from the Faculty of Basic Medical Sciences, Lagos State University College of Medicine, Ikeja; and Faculty of Basic Medical Sciences, Obafemi Awolowo College of Health Sciences, Ikenne, Ogun State stated: “In conclusion, it is proposed that the nephroprotective activities of the aqueous seed extract of the unripe, mature fruits of Carica papaya Linn in carbon tetrachloride-induced nephrotoxicity may involve its antioxidant and/or oxidative free radical scavenging activities.

“Also, the results of this study have confirmed the rationale for the folkloric use of the aqueous seed extract of Carica papaya Linn in the treatment of poison-related renal disorders.”

Antioxidants are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Free radical damage may lead to cancer and kidney damage. Antioxidants interact with and stabilise free radicals and may prevent some of the damage free radicals might otherwise cause.

Carica papaya, which belongs to the Caricaceae family is a perennial, herbaceous plant, with copious milky latex reaching to 6 – 10 meters tall. Its erect stem is about 30 cm thick and roughened with leaf scars. The unripe fruit is reportedly used traditionally among the Yoruba tribe of Nigeria for the treatment of various human and veterinary diseases including malaria, hypertension, diabetes mellitus, hypercholesterolaemia (high cholesterol), jaundice, intestinal helminthiasis and for the management of sickle cell anaemia.

Also, among the Yoruba herbalists, hot infusion of the seeds of the unripe, mature fruits of Carica papaya is employed in the local treatment of poison related renal and hepatic disorders.

Based on the traditional use of Carica papaya seed in the treatment of poison related renal disease, the present study was designed to investigate the effect of graded oral doses (100 – 400 mg/kg/day) and the time-course effect of the aqueous seed extract of mature unripe Carica papaya (CPE) in CCl4 treated rats as a way of validating this folkloric use. The choice of the extract dose range employed in this was based on the result obtained from the orientation study earlier conducted.

It has been shown that various environmental toxicants and clinically useful drugs, like acetaminophen and gentamicin, can cause severe organ toxicities through the metabolic activation to highly reactive free radicals including the superoxides and oxygen reactive species.

Evidence suggests that various enzymatic and non-enzymatic systems have been developed by the cell to cope with the oxidative stress that is associated with reactive oxygen species (ROS) and other free radicals generated. Literature shows that oxidative stress has been implicated in the aetiopathogenesis (the cause and development of a disease or abnormal condition) of CCl4 organ injury and carcinogenesis (cancer-causing).

However, when the oxidative stress is overwhelming, the various inherent defence mechanisms such as the antioxidant defence mechanisms, intracellular concentration of glutathione, superoxide dismutase (SOD) and catalase (CAT) activities become significantly impaired and insufficient.

As a measure of renal function status, serum urea and creatinine are often regarded as reliable markers. Thus, elevations in the serum concentrations of these markers are indicative of renal injury.

In the present study, the dose- and time-dependent nephroprotective effect of the aqueous extract of the unripe seeds of Carica papaya were evaluated in CCl4 induced acute nephrotoxic rats by assessing the effect of the extract pre-treatments on the serum uric acid, urea and creatinine in the CCl4 injected renal injured rats. In addition, the associated histological lesions were studied.

Simultaneous increase in the levels of blood urea, uric acid and creatinine has been observed during a variety of renal disorders.

In the present study, it was observed that treatment with CCl4 induced a significant elevation in the levels of serum uric acid, urea and creatinine within 72 hours of exposure to it.

These biochemical alterations were corroborated by the histological findings of glomerular and tubulo-interstitial necrosis in the untreated model control group. However, daily pre-treatment with CPE for seven days conferred nephroprotection on the CCl4 renal injured rats in a dose-dependent fashion and 400 mg/kg dose offered maximum protection within three hours of exposure to it.

Again, the histological findings of almost normal renal histological architecture corroborate the protection conferred by the extract within the stipulated time interval, especially at the maximum oral dose of 400 mg/kg/day of the extract. Although, the possible mechanism(s) of its protection against CCl4 induced nephrotoxicity was not studied in the current study, it is possible that the protective effect of the extract is mediated through antioxidant and/or free radical scavenging activities.

Literature has shown medicinal plants with nephroprotective properties to mediate their protection via antioxidant and/or free radical scavenging activities due to the high concentration of flavonoids and alkaloids they contain.

Equally, saponins have been reported to protect liver and kidneys against carbon tetrachloride intoxication. In addition, CPE has been reported to contain flavonoids, alkaloids, saponins and other active phytocomponents. Summing these facts, it is plausible for the alkaloid, flavonoid and saponin components of CPE to be responsible for the observed biological effects. These could constitute areas of future research. Again, the nephroprotection offered by the extract could be due to the presence of any of the phyto-principles contained in it.

Nigerian researchers have also shown the antisickling properties of crude juice extracts of the edible portions of three commonly consumed tropical fruits namely Persia Americana (avocado pear), Citrus sinensis (orange) and Carica papaya.

The study was published in African Journal of Traditional Complementary and Alternative Medicines.

The results showed that Ciklavit® produced a sustained reduction in the number of sickle cells in both HbAS and HbSS blood samples. Also, the alkaline and alcoholic extracts of P. americana and C. papaya produced significant reduction in the number of sickle cells.