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B11-P: DETERMINATION OF BORON IN BASIL LEAVES

O. Kovačević, S. Zlatanović, S. Ostojić, L. Pezo, M. Pavlović, B. Simonović

Institute of General and Physical Chemistry, Studenski trg 12/V P.O. Box 551,11000 Belgrade, Serbia

 

Boron is an essential element for plants and beneficial micronutrient for animals and humans. Among other minerals, boron contributes to the strengthening of bones [1]. It has been claimed that boron alleviates some symptoms of osteoarthritis and rheumatoid arthritis. Studies in animals and humans have demonstrated that boron affects calcium and magnesium metabolism, reducing its rate of excretion and increasing serum levels, but the mechanism is uncertain [1, 2]. The richest sources of boron are fruits (3 mg/kg), green vegetables (2 mg/kg), legumes and nuts. Intakes from drinking water are estimated to be 0.2 – 0.6 mg/day [2, 3]. A safe and adequate daily intake of boron is estimated, according to RDA, to be between 1 and 10 mg. The aim of this work is to estimate boron content in basil, which is widely used in functional food diet and Mediterranean nutrition.

The modified EPA 212.3 spectrophotometric method for boron determination was used. Water containing boron was acidified and evaporated in the presence of curcumin, when a red-colored product called rosocyanine was formed proportional to the amount of boron present in the sample. Absorbance measurements were carried out from alcohol solutions, by the spectrophotometar Thermo, type Evolution 600, at 540 nm in a 1 cm cell, against the reagent blank.
The method was modified for the basil plant matrix. Modifications were derived from a series of experiments in the aim to evaluate the manner of basil samples preparation, considering the reaction temperature, time and pH. Methods for boron detection [1-5], in general, have two problems: the sample preparation and reducing matrix interferences. For this purpose, basil was prepared by combustion at 550 oC, during 24 hours. Boron was determined from an alkaline solution in which basil ash was leached.

An internal boron standard was treated in the same way as the basil samples. Results are in accordance to statistic values from unmodified method (STDEV = ±0.02 mg/l). The boron content detected on basil samples, where an internal boron standard was spiked, compared to results of boron content on non spiked samples, gave evidence that the method is valid. The boron content was determined in several commercial dry basil samples, purchased in Belgrade market (Fedela, Kotaniy and Plant Institute Josif Pančić, Belgrade). The ash content in these samples was in the range of 14±1 %, and obtained boron concentrations were in the range of 13 - 22 mg/kg. The ash content in the leaves of fresh basil was 1.5 %. According to that value, estimated boron concentration in fresh basil leaves was in the range from 1.4 to 2.3 mg/kg.

References

1. A. Krejčova, T. Černohorsky, Food Chem., 2003, 82, 303-308.
2. S. Sungur, R. Okur, Food Chem., 2009, 115, 711-714.
3. L. Zaijun, C. Zhengwei, T. Jian, Food Chem., 2006, 94, 310-314.
4. R. N. Sah, P. H. Brown, Plant Soil, 1997, 193, 15–33.
5. Y.-M. Liu., K. Lee., Mar. Chem., 2009, 115, 110 – 117.