Twelve varieties of Mango (Mangifera indica) including Gopal Bhog, Shidura, Him sagar, Misrikanto, Chini Guri, Aamrupali, Lakshmon Bhog, Kali Bhog, Surmi Fajli, Langra, Fajli and Arshini were selected for this study according to their market availability and consumption rate in Bangladesh. Sampling time was during summer (March to May). In order to determine edible portion of fruit, total weight of whole fruit and total weight of roughage were recorded and finally percentage of edible portion was estimated.N-hexane (Analarar grade, BDH, UK). Acetone (Analarar grade, BDH, UK), Activated aluminiumoxide (Brockman activity H,BDH,UK) and Anhydrous sodium sulfate for the preparation of chromatographic column. Standard of Beta–carotene (Sigma chemical USA).Carotenoids were separated from mango extract using a pyrex chromatographic column (2.5x40cm) with sintered glass at bottom. The column was packed with the mixture (alumina, anhydrous sodium sulfate with n-hexane) and made the length 15 cm. n- hexane was passed through the column for few hours to make it stable.Fresh and clean mangoes were chopped and mixed well. From the prepared mixer 2-3 gm was taken in a glass mortar and ground rapidly using a pestle along with 1 to 3 gm of sand, 5 ml acetone and 5ml n-hexane. The liquid was decanted into a 25 ml volumetric flask and the process was repeated 3 to 5 times to make the extract volume 25 ml using n-hexane on each occasion. The flask was stoppered and stored in the dark until analysis. Ten milliliter of the extract was placed on the top of the column bed. The column was run with n-hexane. A deep yellow band containing carotenoid traveled down the column, leaving other pigments xanthophylls, oxidation products, chlorophylls absorbed in to the bed. The column was run until the band was collected. The eluent was made up of a final volume of 25 ml with n-hexane.
Preparation of standard Beta carotene:
Beta carotene of 1 mg was dissolved in 2.0 ml of n-hexane to give an equivalent of 500 microgram/ml. From this solution 20 micro liters were diluted to 10 ml to have a solution equivalent to 1mg/ml. Absorbance of this solution was taken at 450 nm in spectrophotometer using extinction coefficient value of beta-carotene then solution was made 1mg/ml. The absorbance of this solution was recorded 0.27.
Recording absorbance of the extracted solution:
Carotenoids show characteristics absorbance spectra, for example beta carotene has an absorption maximum of 450 nm in n-hexane with a molecular extinction coefficient of 2592. Therefore to estimate the total carotenoid in the eluent, absorbance of it was read on a spectrophotometer at 450 nm using a 1cm cell.
The total carotenoid concentrated is calculated using the formula below:
Total carotenoid content (μg/g):
A = Absorbance at 450 nm
Volume = Total volume of extract (25 or 50 ml)
A 1%-cm = Absorption coefficient of β-carotene in petroleum ether (2592)