Table 9 other therapeutic properties of some peels and seed extracts

Tangerine peel

Tangeretin

Rats

(50 mg/kg)

rheumatoid arthritis protection

Decreased the oxidative stress damage through decreasing the IL-1β, TNF-α, IFN-γ, and PGE2 levels, regulates inflammatory cytokine expression, suppression of the accumulation of MDA products, enhancing the IL-10 and the activity of antioxidant enzymes through upregulation of Nrf-2 signaling pathway.

[150]

Apple peel

Ursolic acid

Mice

(50 mg/kg)

rheumatoid arthritis

decreased the levels of stress mediators related to synovial inflammation, such as KC/CXCL-1 levels by 95%, TNF-a levels by 76%, and IL-1b levels by 57%,

[125]

A. comosus fruit peel

Flavonoids, tannins, triterpenoids and phytosterols

Freund’s adjuvant rat

500 mg/kg b.w.

Anti-rheumatic activity

Rat paw swelling reduction, increased levels of SOD, CAT and GPx in liver, kidney and spleen, and reducing the levels of C-reactive proteins (CRP) and prostaglandins (PGE2) in serum of arthritic rats.

[149]

Potatoes peel

phenolic compounds and glycoalkaloids caffeic acid chlorogenic acid, tryptophan, α-solanine, α-chaconine, tyrosine

Mice cell based assays

10 and 20%

Antiobesity/ Supplement for weight loss

decreased expression of the gene for fatty acid synthase, less fat storage, as indicated by a reduced expression of the stearoyl-CoA desaturase-1gene, reduced transcription of the insulin-responsive glucose transporter and reduced transcription of the lipoprotein lipase gene

[152]

C. sinensis × Poncirus trifoliata (citrange) fruit peel

neoeriocitrin, narirutin, naringin, hesperidin, neohesperidin, poncirin, naringenin, nobiletin and tangeretin.

Female mice

1% w/w

Ameliorate obesity

The down-regulation of expression level of peroxisome proliferator-activated receptor γ PPARγ) and its target genes, Reduction of the expression levels of liver X receptor (LXR) α and β, which are involved in lipid and glucose metabolism

[153]

immature Citrus sunki peel

Ameliorate obesity

increased β-oxidation and lipolysis in the adipose tissue of high fat diet-induced obesity mice

[151]

pomegranate seed oil

linolenic acid,

Mice

decreased weight gain

higher levels of leptin, lower levels of adiponectin

[66]

Mimusops balata peel and seed

Taxifolin

Mice

300 mg/kg

antiulcerogenic activity

gastric volume reduction, pH, total acidity, and pepsin activity in the gastric juice maintained GSH levels, reduction of LPO content, inhibition of neutrophil migration

[154]

Banana (M. sapientum L.) peel

7,8-dihydroxy-3-methyl-isochromanone-4

Rats

antihypertensive activity

ACE inhibitor

[137]

purple passion fruit peel

Quercetin, edulilic acid

Humans

150 mg/d

reduces wheeze and cough and improves shortness of breath in adults with asthma

Nitric oxide lowering effect, inhibit histamine release, arachidonic acid metabolism, and cytokine production

[20]

Orange peel

Hesperidin

Human skin keratinocyte line HaCaT cells

220 μg/ml)

Photoprotection, anti-oxidative and anti-inflammatory capacities in skin injuries

Reduced UVA-induced oxidative stress and inflammatory response, elevate SOD activity and significantly decreased MDA content and increased the total antioxidative capacity levels

[141]

litchi and rambutan peel and tamarind seed

Phenols

B16F10 melanoma cells

0.25 mg/ml

0.0001–0.01 mg/ml

skin aging treatment

Extracts suppress melanin production in B16F10 melanoma cells through inhibition of tyrosinase and TRP-2

[139]

Citrus limetta Risso peel

flavonoids, carotenoids, dietary fiber, sugars, polyphenols, essential oils, and ascorbic acid

mice/cell lines

20 μL/ear/time

alleviates skin inflammation

reduced lipid peroxidation, the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ear thickness, ear weight, pro-inflammatory cytokines production and ameliorate the histological damage in the ear tissue

[119]