Fruit and vegetable peels: Paving the way towards the development of new generation therapeutics.

Cardiovascular diseases (CVDs), diabetes mellitus (DM), cancer, and thyroid abnormalities are major health problems prevalent around the world and are responsible for a large portion of morbidity and mortality out of health problems overall. Advances in genomics and proteomics in recent years have led to an explosion in the number of possible therapeutic targets and drug candidates through use of molecular approaches, chemical synthesis, traditional medicinal chemistry, and phyto-chemistry and through the exploration of novel herbal preparations. However, virtually none of these candidates are devoid of potential adverse drug reaction(s) or undesirable side effects. Therefore, the clear need is to look to alternative ways to develop novel drug candidates with fewer side effects and less cost. Interestingly, the last few years have seen an increase in the number of available reports on fruits and vegetable peels, and particularly on their biological activity, their content of different bioactive compounds, their chemical characterization, understanding of their structure-activity relationships, isolation and purification of commercially important chemicals without using high throughput techniques, etc. Therefore, research in the field of fruit and vegetable peels should present immense possibilities for drug discovery and development of cost-effective therapies that have fewer or practically no side effects. This virtual explosion of interest in fruit and vegetable peels as a source of medicinal and nutritional value has led to the present review.

Comparative analysis of free radical scavenging potential of several fruit peel extracts by in vitro methods.

We studied the radical scavenging potential of several fruit peel extracts using various standard chemical and biochemical in vitro methods. Peel extracts of C. sinensis (CS), P. granatum (PG), M. paradisiaca (MP), C. vulgaris (CV), C. melo (CM), M. indica (MI), and C. papaya (CP) were used in the present study and butylated hydroxyl anisole (BHA) was used as a standard. Marked 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was observed with 25 µg/mL of CS and MP and 50 µg/mL of PG, while all the studied doses of CP were found to be pro-oxidative. ß-Carotene bleaching revealed a higher singlet oxygen scavenging potential of all the peel extracts except MI. High NO-radical scavenging activity was observed at 25 µg/mL of PG and MP. Inhibition test of H2O2-induced LPO in erythrocytes or in liver tissue showed that all the peels tested were effective on peroxy-radicals at one or other doses. The present study revealed the radical scavenging activity of the test peel extracts in a manner that was dose- and radical/methodspecific. Therefore, evaluation of the efficacy of herbal extracts should be carried out using different methods and not merely a single in vitro method.

Antiperoxidative, antithyroidal, antihyperglycemic and cardioprotective role of Citrus sinensis peel extract in male mice.

An extract of Citrus sinensis (CS) peel was evaluated for its efficacy in ameliorating L-thyroxine (L-T(4)) induced tissue lipid peroxidation (LPO), hyperthyroidism and hyperglycemia in mice. In a preliminary investigation, of the three different doses of CS (12.5 mg/kg, 25 mg/kg and 50.0 mg/kg) peel extract, 25 mg/kg was found to be the most effective and antiperoxidative, while 50 mg/kg was proved to be hepatotoxic. Therefore in the pilot experiment the effects of 25 mg/kg/day of CS for 10 days were studied in L-T(4) induced hyperthyroid animals. L-T(4) (500 microg/kg/day for 10 days) increased the levels of thyroxine (T(4)) and triiodothyronine (T(3)) with a concomitant increase in serum glucose concentration, alpha-amylase activity, heart/body weight ratio (HW/BW), kidney/body weight ratio (KW/BW) and cardiac as well as hepatic LPO. However, it decreased the concentration of different serum lipids such as total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C). Administration of CS extract (25 mg/kg/day) in hyperthyroid animals reversed most of these observations revealing the ameliorating potential of CS extract against various adverse effects of hyperthyroidism. It appears that the test extract primarily acts through its antioxidative/free radical-scavenging, antithyroidal and HDL-C stimulating properties.

Cardio-protective role of Terminalia arjuna bark extract is possibly mediated through alterations in thyroid hormones.

Terminalia arjuna bark extract is believed to exhibit cardio-protective effects. In the present study we investigated the possible involvement of thyroid hormones in the amelioration of cardiac and hepatic lipid peroxidation (LPO) by a bark extract of the plant in albino rats. While L-thyroxine (L-T4) treatment increased the level of thyroid hormones, heart/body weight ratio as well as cardiac and hepatic lipid peroxidation, simultaneous administration of 21.42 and 42.84 mg/kg of the plant extract decreased the level of thyroid hormones and also the cardiac LPO, suggesting the possible mediation of the drug action through an inhibition in thyroid function. These effects were comparable to a standard antithyroid drug, propyl thiouracil (PTU). When the drug was administered to euthyroid animals, serum concentrations of thyroid hormones were decreased, whereas the hepatic LPO increased indicating a drug induced toxicity in euthyroid subjects. Although a suboptimal dose of the drug was found to be non-toxic to the liver, it appeared to be of no use, as it could neither affect the thyroid functions nor the cardiac lipid peroxidation. Since in euthyroid animals, thyroid hormones were decreased and hepatic LPO was increased, it is suggested that high amounts of this plant extract should not be consumed, as hepatotoxicity as well as hypothyroidism may be caused.