Chlorophyll Extraction and Storage Studies on Selected Vegetables (Bitter Leaf - Vernonia Amygdalina, Pawpaw Leaf - Carica Papaya and Pumpkin Leaf - Telfairia Occidentalis)

Abstract

Chlorophyll is the term used for several closely related pigments found in cyanobacteria and the chloroplast of algae and plants. Chlorophyll is the green pigment responsible for the color of leaves. Its presence in leaves is crucial for photosynthesis. Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. Conversely, it is a poor absorber of green and neargreen portions of the spectrum, hence the green color of chlorophyll containing tissues. This study evaluated the effect of extraction solvent and storage on chlorophyll extracted from selected vegetables (bitter leaf, pawpaw leaf and pumpkin leaf), It also observed the absorbance pattern at 430nm for chlorophyll a and 660nm for pheophytin a (a derivative of chlorophyll) for extracts stored at room temperature and water activity(aw) of 0.33 and 0.75 during a one month storage period. Uv-visible scans were carried out weekly for all extracts during the storage period. Absorbance measurement at 430nm and 660nm showed that initially, after extraction, the absorbance values of extracts followed according to the order of polarity of the solvents used for extraction. The order of polarity was deionized distilled water > ethanol > acetone > petroleum ether > nhexane. Uv-visible scan for extracts stored at room temperature, initially after extraction and after one month storage period showed the dominant presence of chlorophyll a and chlorophyll b. Uv-visible scan for extracts stored at water activity(aw) of 0.33 showed the conversion of chlorophyll b at 467nm,473nm to chlorophyll a at 448nm,671nm after one month storage period and conversion of chlorophyll a to an unknown compound which absorbs at 331nm or 333nm. Uv-visible scan for extracts stored at water activity (aw) of 0.75 showed the conversion of chlorophyll a and chlorophyll b to an unknown compound which absorbs at 331nm or 333nm. The pH measured for extracts stored at water activity (aw) of 0.33 showed increase in acidity after one month of storage. pH measured for extracts stored at water activity (aw) of 0.75 showed pH change to slightly alkaline except for pawpaw leaf extracts which showed increase in acidity. The difference between the initial and final specific gravity shows reduction in the chlorophyll content of extracts after one-month storage period. Chlorophyll Extraction and Storage Studies on Selected Vegetables (Bitter Leaf Vernonia Amygdalina, Pawpaw Leaf Carica Papaya and Pumpkin Leaf Telfairia Occidentalis) International Journal of Advanced Research in Chemical Science Page | 41 Chlorophyll was first isolated by Joseph BienaiméCaventou and Pierre Joseph Pelletier in 1817. In an extraction by Zvezdanoicet al, (2009), Fresh plant leaves were first depleted from the mid ribs and washed with cold water. The extraction and re-extraction mixtures were methanol and petroleum ether in a 2:1 ratio, and petroleum ether and diethyl ether (1:1), respectively. Chlorophylls belong to the group of the most important bioorganic molecules; they are the principal pigments in photosynthesis, capable of light energy absorbing and its conversion to “chemical energy” by the formation of chemical compounds rich in energy (needed for the biosynthesis of carbohydrates and other compounds in photosynthetic organisms such as plants, algae and photosynthetic bacteria (Scheer, 1991 and 2006).The chlorophylls comprise a group of more than 50 tetrapyrrolic pigments with common structural elements and function (Scheer, 2006).