Document heading
Effect of hydrothermal processing on total polyphenolics and antioxidant potential of underutilized leafy vegetables,Boerhaavia diffusa and Portulaca oleracea
- Open Access funded by Hainan Medical University
- Under a Creative Commons license
Open Access
ABSTRACT
Objective
To investigate the effect of different processing methods on antioxidant properties of acetone extract of aerial parts from Boerhaavia diffusa and Portulaca oleracea.
Methods
The total phenolic and flavonoid contents were determined by Folin-Ciocalteau and aluminum chloride method, respectively. FRAP, metal chelating activity, DPPH, ABTS, nitric oxide, hydroxyl and superoxide radical scavenging activities, carotene/linoleic acid bleaching activity were used for the determination of antioxidant capacity.
Results
The total phenolics in Boerhaavia diffusa (82.79–162.80 mg GAE/g extract) were found to be higher when compared to that of Portulaca oleracea (22.94–10.02 mg GAE/g extract). Hydrothermal processing enhanced the level of inhibition on synthetic radicals such as DPPH (3 439–309 549 mmol TE/g extract) and ABTS (17 808–53 818 mmol TE/g extract) as well as biologically relevant radicals such as superoxide anion (70%-90%) and nitric oxide (49%-57%). In addition, boiling of the vegetables were found to be maximum capacity of FRAP (6 404.95 mmol Fe (II)/g extract) and metal chelating activity (1.53 mg EDTA/g extract) than the respective raw samples.
Conclusions
The present investigation suggests that the processing enhance the functionality and improves the availability of bioactive substances of these vegetables. In addition, they also exhibited more potent antioxidant activity. Therefore these natural weeds from the crop land ecosystem could be suggested as cost effective indigenous green vegetables for human diet and potential feed resources for animals. Further extensive studies on role and importance of those weeds in sustaining the agro biodiversity are also needed.
KEYWORDS
- Boerhaavia diffusa;
- Portulaca oleracea;
- Green vegetables;
- Boiling and bleaching;
- Phenolics;
- Antioxidant capacity.
1. Introduction
Unlike in ancient times, nowadays the diet in India is mainly based on rice as in many other tropical Asian countries and the consumption of fruits and vegetables have been reduced. In India National survey reveals that around 95% of the adult men and women have high prevalence of diabetes due to low intake of fruits and vegetables particularly neglecting of indigenous fruits and vegetables. Therefore, it is important to revise and follow the food habit based on the traditional diet. In ancient period, people used a variety of indigenous fruits and vegetables in their daily diets. Among the different vegetables, the leafy vegetables play an integral part in their diet. In addition to serving as an important source of minerals, they are also provided provitamin A, carotenoids, folate, and linolenic acid. Nowadays in India the consumption of leafy vegetables has decreased over the years and highly variable depends on factors such as degree of urbanization, adequate availability, seasons and also the taste of the indigenous leafy vegetables, which are inferior to exotic vegetables such as cabbage and spinach[1]. However, traditional green leafy vegetables are rich source of phytochemicals which improves functionality and health benefits of food. Diet rich in fruits and vegetables have long been associated with reduced risk of chronic disease such as obesity and cardiovascular disease. Recently scientists pay more attention on using available experimental techniques, to identify the natural antioxidants from plants along with nutrients which provide new remedies to mankind. In order to enhance the current nutrition education, knowledge of the nutrient composition and its usage in nutraceutical action of the traditional vegetables is essential. Boerhaavia diffusa (B. diffusa) andPortulaca oleracea (P. oleracea) are the most common traditional leafy vegetables which have a long history of use by indigenous and tribal people of India and by many other countries.
B. diffusa is an herbaceous weed, commonly known as ‘Punarva’, is the member of Nynctaginaceae family. It is widely used by tribal people in Uttar Pradesh and Madhya Pradesh for the treatment of rheumatism, leucorrhea, stomach ache and elephantiasis. In the Indo-Nepal Himalayan terrain, the tribal peoples harvest this plant for medicinal purposes mainly for flushing out the renal system, to treat seminal weakness and blood pressure[ 2]. The plant contains several bioactive compounds-flavonoids, alkaloids, steroids, triterpenoids, lipids, lignins, hypoxanthine 9-Larabinofuranoside, ursolic acid, lirodendrin, and glycoprotein that have been accredited to diverse pharmacological properties. Many rotenoids known as boeravinones (A-F) have also been isolated from the roots of the B. diffusa[ 3]. Previous studies have reported that parts of B. diffusa such as root, leaf extracts exhibit a wide range of medicinal properties such as anti-inflammatory, diuretic, laxative, antiurethritis, anticonvulsant, antinematodal, antifibrinolytic, antibacterial, anthelmintic, antileprotic, antiasthmatic, antiscabby and antistress, hepatoprotective, antioxidant, antinociceptive, antibacterial and antidiabetic[3]. Further, it is also used as a kidney rejuvenating drug and as an excellent natural remedy for urinary track diseases[ 4]. The leaves and immature fruits are found to be a potential feed source for birds and poultry. Due to the presence of high nutrition, palatability and non-toxic factors, such weed plants are being grazed by sheep, goats and cows from agroecosystem. Interestingly in West Bengal, it is believed that the plant improves the milk yield when fed to the dairy animals[ 5].
P. oleracea, an herbaceous member of family Portulacaceae, is also known as purslane, Verdolaja, Karikkirai, Brihalloni, Chota Lunia. There are several species of genusPortulacaceae which are distributed in tropical, subtropical and temperate regions throughout the world like Africa, Australia, Euroasia, South America, and North America. It has been in use since ancient times by indigenous and tribal people of Europe, Africa, United States, China, India, and also in Australia[ 6]. The preliminary screening of the P. oleracea plant revealed that the presence of protein, soluble carbohydrate, inorganic acids, alkaloids, flavonoids, coumarins, cardiac glycosides, anthraquinone glycosides, saponin and tannins[ 7]. The leaves are reported to have high amount of iron, omega-3 fatty acids, and α-linolenic acid[ 8]. The most interesting metabolites, from the therapeutic point of view, ω-3 fatty acid from different parts of P. oleracea plays a major role in the regulation of inflammation controlling gene products[ 8]. The stem, leaves and the whole plant of P. oleracea have been employed for the treatment of scorpion sting and also used as antihelmintic, cooling or moistening agent for fever, etc. The pharmacological studies have been demonstrated that the aerial parts of P. oleraceaexhibit a wide range of properties such as nephrotoxicity[ 9], hepatoprotective[ 10], antioxidant[ 11], and neuroprotective[ 8], etc. Moreover, presence of secondary metabolites makes this plant medically more important to be exploited by clinicians and scientists to gain more insight into its biological and medicinal properties[ 7].
Many research investigations revealed that the retention of adequate bioactive components in the food material even after subjecting under various cost effective indigenous processing methods could supply the potential nutrient and nutraceuticals. Several studies have been reported that the high antioxidant properties of B. diffusa Linn and P. oleracea[ 2, 3, 11 and 12]. However, there are no studies on the effect of processing on antioxidant activities of these indigenous vegetables. Therefore, the present study aimed to estimate the effects of different processing methods, like boiling and blanching, on the total phenolics, tannins, total flavonoids and antioxidant activity ofB. diffusa and P. oleracea. Results from this preliminary study may provide a better understanding of the antioxidant properties of this plant for developing value-added foods and neutraceuticals.
