INTRODUCTION:

The “functional food” industry has produced and marketed foods enriched with bioactive compounds, but there are no universally accepted criteria for judging efficacy of the compounds or enriched foods.²

Food is any substance consumed to provide nutritional support for human body. There are around 2,000 plant species are cultivated for food³

Recent advances in drug therapy has tremendously increased due to its demand with the ever growing health care needs. Occurrence of many dreadful diseases including liver, kidney, heart disorders are now a day’s very common and people prefer modern medicines as compare to conventional medicines. But Scientific knowledge and exploration and technological advancements had made plant derived medicine as a choice of therapy in many ailments⁴

Plants produce secondary metabolites termed in general as ‘phytochemicals’ having the potential to combat diseases such as cancer, heart stroke or metabolic syndrome. They are non-essential nutrients and possess certain properties like antioxidant, antimicrobial and immune modulating activities⁵

Vegetable is an important contributor to human diet and are good source of carbohydrate including starch and cellulose, large amount of vitamins folic acid, vitamin A and vitamin C⁶

The main problem in nutritional exploitation of green leafy vegetable is the presence of anti-nutrients. Oxalate is one of the organic compounds found in plants and is an antinutrient. Oxalate is associated with metabolic disorders and infectious diseases^7,8 The oxalate content of plants can vary according to their age, the season, the climate and the type of soil. In some plants, such as Rhubarb, oxalate content tends to increase as the plants mature, whereas, in other plants, e. g. Spinach, sugar beet leaves, and bananas, there is a large increase in oxalate content during the early stages of development, followed by a decrease as the plants mature⁹. In plants oxalates play role in ion balance, plant defense, tissue support, detoxification, light gathering and reflection¹⁰

The population of Syria has food habits, they consume some of the vegetable as raw salads and some are in boiled form.

Usually vegetable accumulate high amount oxalates. Consumption these vegetables in raw or boiled form can deposit large amounts of plant oxalates and its absorption can be fatal to both humans and animals; it causes oxalosis¹¹. Human urine always contains small levels of calcium oxalate; excess oxalates in body can trigger to increase urinary oxaltes that may be deposited in the kidneys as common form of kidney stones^12,13 Kidney stones are aﬀect people who are between 30 and 60 years of age. They aﬀect men more than women. It is estimated that renal colic (severe pain caused by a kidney stone) aﬀects about 10-20% of men, and 3-5% of women. In India, 12% of the population is expected to have urinary stones, out of which 50% may end up with loss of kidneys or renal damage¹⁴

Urinary stone disease occurs worldwide with some geographical and racial variation and is constantly rising in parallel with socio-economic development1.it is largely a recurrent disease with an approximate relapse rate of 50% in 5-10 years and 75% in 20 years¹⁵ also Urinary stones are highly prevalent in India as it affects 15% of population which leads to loss of one or both kidneys. Northern part of India encounters 15% cases suffering from kidney stones¹⁶

Calcium containing stones, especially calcium oxalate monohydrate, calcium oxalate dihydrate and basic calcium phosphate are the most commonly occurring ones to an extent of 75-90% that is followed by magnesium ammonium phosphate (Struvite) to an extent of 10- 15%, uric acid 3-10% and cysteine 0.5-1%. In most of the cases the commonly occurring stones are calcium oxalate or magnesium ammonium phosphate type.¹⁷

Sometimes it can cause acute renal failure in About 75%¹⁸ of all kidney stones are composed primarily of calcium oxalate¹⁹ and hyperoxaluria is a primary risk factor for this disorder^20,21 Restriction of dietary oxalate intake has been proposed to prevent the formation of calcium oxalate kidney stones.

Cabbage is a popular vegetable with storage of phytochemicals namely thiocyanates, indole-3-carbinol, lutein, zeaxanthin, sulforaphane, and isothiocyanates and it is an excellent source of natural antioxidant also it is rich in essential vitamins such as vitamin B5, vitamin B6 and vitamin B1 along with adequate amount of essential minerals like iron, potassium, manganese and magnesium.²² it is listed itself as the most exported vegetable commodities compared to other types of vegetables²³

Spinach (Spinacia oleracea L.) is an edible flowering plant in the family Amaranthaceae. It is most probably a native of central and western Asia region. It was known in China as early as 647 AD²⁴

Parsley has been used as carminative, gastro tonic, diuretic, antiseptic of urinary tract, anti-urolithiasis, anti-dote and anti-inflammatory and for the treatment of amenorrhea, dysmenorrhea, gastrointestinal disorder, hypertension, cardiac disease, urinary disease, otitis, sniffle, diabetes and also various dermal disease in traditional and folklore medicines²⁵

MATERIAL AND METHODS:

Sample Collection Ten vegetable samples for each plant were selected from the local market in Syria for determination of oxalate content.

The selected samples were Spinach (Spinacia oleracea), Cabbage (Brassica oleracea var. capitata), parsley (Petroselinum crispum)

Preparation and analysis of sample: All the selected samples were packed in a clean polyethylene bags and transferred to laboratory for processing. The samples were divided into two parts, 100g of clean sample was dried directly in an oven at a temperature of (450C) and another 100g of sample was boiled for 15 minutes in fresh water then the samples were kept in oven for drying at temperature of (450C) for 24 hours. After drying all the samples were pulverized to a uniform particle size and packed in an airtight container for further analysis.

Titration using KMnO₄:

The oxalate content in all the samples were analyzed by following titration method using KMnO₄ described in AOAC²⁶. In the determination of oxalate, 1g of each selected vegetable samples were weighed and mixed with 20 ml 0.1M HCl in a 50ml beaker to extract total oxalate and another 1g of each selected samples were weighed and mixed with 20ml of distilled water to extract soluble oxalate.

All beakers with samples and extracting solvents were kept in a water bath at 100oC for 30 minutes, later filtrated using Wattman No 1 filter paper. 0.5ml of 5% Calcium chloride was added to the filtrate to precipitate out Calcium oxalate, the precipitate was separated by centrifugation at 3500 rpm for 15 minutes, and supernatant was discarded. The Calcium oxalate precipitate was washed with 2ml of 0.35M Ammonium hydroxide and then dissolved in 0.5M of Sulphuric acid. The dissolved solution was titrated with 0.1M of Potassium Permanganate at 600C till faint pink color was persisted for at least 15 seconds. The oxalate content was calculated by using stoichiometric formula.

The soluble oxalate was subtracted from total oxalate to obtain insoluble oxalate; both soluble and insoluble oxalates were expressed on dry weigh basis (DW).

RESULT AND DISCUSSION:

The total oxalate, soluble oxalate and insoluble oxalate content of the selected ten samples were expressed in mg/100g of dry weight. The oxalate content of unboiled and boiled samples with percentage of reduction is given in table 2:

Table 1: Names of samples investigated in the present study

Name Part of Plant	English Name	Scientific
Leaf	Spinach	Spinacia oleracea
Leaf	Cabbage	Brassica oleracea
Leaf	Parsley	Petroselinum crispum

Total oxalate content of the selected vegetable on dry weight basis of unboiled or raw samples was ranged from 191.08mg to 1466.82 mg/100g. The lowest amount of total oxalate content (191.08mg/100g) was found B. olerace and the highest was in P. crispum (1466.82mg/ 100g) followed by S. oleracea (478.7mg/100g)

In pervious study total oxalate was determined from B.oleracea collected from Nigeria contains 225mg of total oxalates/100g of sample. But the same species investigated in the present analysis has reported lower amount of total oxalates (189mg/100g) of dry weigh. The composition of nutrients and anti-nutrient in plants may vary depending on the variety and growing conditions²⁷. It is noticeable that each of the leaves can accumulate high in one or two anti-nutrient and low in another²⁸. The lowest level of total oxalate in boiled samples was obtained from B. oleracea (135.94mg) followed by P. crispum (251.19mg) per 100g respectively S. oleracea (285.68mg) recorded the high values of total oxalate in boiled samples. Boiling has shown effect on oxalate content of all the samples investigated in the present study. The percentage of reduction of total oxalates was ranged from 5.85% to 40.32%.

P. crispum has shown least percentage of reduction while S. oleracea has reported with highest percentage of reduction.²⁹ have noticed the variation in phytochemical contents of fresh fruits and vegetables include genetics, species of plant, and stage of growth, harvesting and postharvest handling during storage.

In SYRIA Spinach and Parsley are highly consumed vegetables; Cabbage IS eaten as raw vegetables as vegetable salads and the other analyzed vegetables are eaten as cooked form. Therefor the mean lethal dose of oxalates for an adult is 15 to 30g, and the lowest reported lethal dose is about 70mg/kg body weight³⁰.

Recent reports showed that the diet with high oxalates can interfere with calcium absorption in kidney and increase the possibilities to form kidney stones³¹.

However, the critical factor in stone formation does not necessarily correspond with oxalate content³². certain foods such as Spinach and Cabbage have high oxalate content but the bioavailability is low. Therefore though P. crispum is having high oxalates (1466.82mg/100g), the possibilities to cause kidney stones are low. The same sample in the present investigation has shown maximum percentage of reduction (28.33%) on cooking.

CONCLUSION:

All the samples investigated in the present study contains considerable amount of both soluble and insoluble oxalate. The boiling of samples for 15 minutes have shown great reduction in the concentration of soluble oxalate and in-soluble therefore total oxalates in some samples like Spinacia oleracea. showed highest amount of reduction of oxalate after boiling the samples. Usually low oxalate diet should contain 50mg/100g and is the recommended daily intake per day. Too much of oxalate in food combine with endogenously synthesized oxalates to form urinary oxalates results in the formation of kidney stones. High concentration of oxalates in the body also prevents the absorption of soluble calcium ions and the oxalate bonds with the calcium ions to form insoluble calcium oxalate complex. Therefore, people who have tendency to form kidney stones should avoid oxalate-rich foods and if they want to take this food they should boil it.

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Received on 30.12.2020 Modified on 13.01.2021

Research J. Pharm. and Tech 2021; 14(10):5341-5344.

DOI: 10.52711/0974-360X.2021.00931

Scientific Name	Unboiled Samples(mg/100g)			Boiled Samples(mg/100g)			% Reduction of total oxalate
Scientific Name	Insoluble Oxalate	Soluble Oxalate	Total Oxalate	Insoluble Oxalate	Soluble Oxalate	Total Oxalate	% Reduction of total oxalate
S. oleracea	163.5	315.2	478.7	33.52	252.16	285.68	40.32%
B. olerace	96.52	94.56	191.08	72.8	63.14	135.94	28.85%
‎P. crispum	590.31	876.51	1466.82	395.58	655.61	1051.19	28.33%