Abstract
Okra (Abelmoschus esculentus (L.) Moench), a healthy vegetable, is widely spread in tropical and subtropical areas. Previous studies have proven that okra pods possess anti-fatigue activity, and the aim of this research is to clarify the anti-fatigue constituents. To achieve this, we divided okra pods (OPD) into seeds (OSD) and skins (OSK), and compared the contents of total polysaccharides, total polyphenols, total flavonoids, isoquercitrin, and quercetin-3-O-gentiobiose and the antioxidant activity in vitro and anti-fatigue activity in vivo between OSD and OSK. The contents of total polyphenols and total polysaccharides were 29.5% and 14.8% in OSD and 1.25% and 43.1% in OSK, respectively. Total flavonoids, isoquercitrin and quercetin-3-O-gentiobiose (5.35%, 2.067% and 2.741%, respectively) were only detected in OSD. Antioxidant assays, including 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, ferric reducing antioxidant power (FRAP) and reducing power test, and weight-loaded swimming test showed OSD possessed significant antioxidant and anti-fatigue effects. Moreover, biochemical determination revealed that that anti-fatigue activity of OSD is caused by reducing the levels of blood lactic acid (BLA) and urea nitrogen (BUN), enhancing hepatic glycogen storage and promoting antioxidant ability by lowering malondialdehyde (MDA) level and increasing superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) levels. These results proved okra seeds were the anti-fatigue part of okra pods and polyphenols and flavonoids were active constituents.
Highlights
Fatigue is a complex physiological phenomenon, which is defined as difficulty in initiating or sustaining voluntary activities [1]
There are several theories about the causes of fatigue, such as exhaustion theory, which states fatigue is caused by a lack of available ATP for actin-myosin coupling, Na/Kpumping and Ca2` uptake by the sarcoplasmic reticulum [8,9,10,11]; homeostasis disturbance theory, which indicates fatigue is caused by the accumulation of various metabolic byproducts [10,12]; and catastrophe theory indicating that fatigue may develop due to failure at one or several sites along the pathway of force production [13]
We divided the fresh okra pods into seeds and skins, and compared the chemical contents of total polysaccharides, total polyphenols, total flavonoids, isoquercitrin and quercetin-3-O-gentiobiose, and antioxidant activities in vitro and anti-fatigue activities in vivo between okra seeds and skins. All these results revealed that okra seeds were the anti-fatigue part of okra pods, and polyphenols and flavonoids were active constituents
Summary
Fatigue is a complex physiological phenomenon, which is defined as difficulty in initiating or sustaining voluntary activities [1]. Apart from increasing with age and presenting in cancer, depression, HIV infection, multiple sclerosis and Parkinson’s disease patients, fatigue is becoming a more and more common symptom in normal humans with the increasing pace of modern life [2,3,4]. Long-term accumulated or chronic fatigue lowers the quality of life, and leads to chronic-fatigue syndrome and other organic illnesses, and even leads to karoshi (the abnormal death from acute cardiovascular diseases caused by overwork [7]). Oxidative stress is widely thought to play an important role in the etiology of fatigue [10,13,14,15,16]. Consumers are seeking more natural antioxidant components in their diet to reduce oxidative damage and fight against fatigue
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