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Goa University research led by Dr. Nandkumar Kamat shows that fresh Kokum juice could be a potential souce for organic UV protection sunscreens
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Potential Biotechnological Applications of UV Absorbing pH Sensitive Pigments in
Kokum (Garcinia indica Choicy)
Nandkumar M. KamatDepartment of Botany, Goa University, Taleigao,
Goa.
Garcinia indica Choisy
INTRODUCTION• Plant Anthocyanins are pigments serving as UVscreen and may be present in entire fruit, juice orconfined only to skin (Goodwin, 1976).
• Garcinia indica Choisy or Kokum is a tropicalevergreen, slender ornamental tree havingcommercial importance with variety of culinary andmedicinal uses.
• Oval, ripe, dark red Kokum fruits containanthocyanin pigments like cyanidin-3-glucoside andcyanidin-3-sambubioside(http://www.hvfl.com/kokum.htm).
♦ Strawberry anthocyanins have been found to beextremely sensitive to fluctuations in pH and athigher pH colour is lost (Goodwin, 1976).
♦ The pH buffering capacity of Kokum is wellknown (http://buyersguide.ift.org/cms).
♦ However, there is relatively poor knowledge of theeffect of changing pH on the colour of the kokumjuice.
♦ This work was aimed to assess the effect of theincreasing pH on the colour and the UV-visiblespectroscopic absorption profile of the Kokum juicein view of the possibility of the application of thefindings in biotechnology.
Habit of Kokum Different stages of fruit maturation
Ripe red fruits Dry Kokum rind
OBJECTIVES• To assess the impact of pH changeon the colour of the fresh Kokumjuice• To assess any correspondingchange in UV-Visible spectroscopicprofile• To identify distinct UV-Visiblespectral absorption peaks associatedwith the pH and /or colour change• To evaluate the potential of theresults for appropriate commercialand biotechnological applications
MATERIALS AND METHODS Freshly harvested ripe Kokum fruits were washed thoroughly under tap water
Juice squeezed mechanically with muslin cloth
Centrifuged at 5000 rpm for 20 minutes
Five ml juice aliquot diluted to 25 ml with double distilled water
Original pH (Control Dynamics digital pH meter APX 175) and colour (Camel shade card) recorded
Titrated against 0.5 N NaOH till a distinct colour change appeared
pH, spectral profile for each colour change noted
Spectral profile was recorded using Shimadzu double beam UV spectrophotometer (Shimadzu) in range of 190-750 nm, in matched Quartz cuvettes with dist. water as ref.
A sample of freshly extracted Kokum juice
RESULTSTable 1: pH and colour change
Sr No. pH Colour change Colour code1 1.87 Alizarin crimson 0022 1.99 Vermilion hue 4493 2.85 Cadmium red 0414 4.70 Gold ochre transparent 1725 5.25 Raw sienna 3666 6.16 Raw sienna 3667 7.46 Venetian red 4478 8.47 Venetian red 4479 10.56 Venetian red 44710 13.00 Cadmium orange 039
♦ It was observed that the original red colour of the juice changed tocadmium orange within a pH range of 1.87-13.00
♦ pH 5.25 and 6.16 showed raw sienna with a slight variation in colour.Similarly for pH 7.46, 8.47 and 10.56.
♦ After pH 13.00 the colour did not change further.
Flasks exhibiting some colours produced by change in the juice pH. Generally at lower pH the shades are closer to pink and with alkaline conditions these shift to Orange
RESULTSTable 2: pH and spectral profile
Spectral peaksSr. No. pHWavelength(nm)
Absorbance
1 1.87 265.50208.50
1.1083.972
2 1.99 264.00193.00
0.2492.488
3 2.85 262.00193.00
0.2152.408
4 4.70 193.50 2.5685 5.25 194.00 2.5406 6.16 194.00 2.6197 7.46 194.00 2.6078 8.47 194.00 2.6559 10.56 194.50 2.64010 13.00 203.50 3.280
RESULTS♦Two peaks are observed at pH 1.87, 1.99 and 2.85, each with one major peak in the range of 193.00 to 209.00 nm.
♦The minor peak with less absorption diminishes from pH 1.87 to 2.85 from 265.5, 264.00 to 262.00 nm respectively and completely disappears at higher pH.
♦pH 5.25 to 8.47 shows a common peak at wavelength 194.00 nm with slight variation in absorption.
♦There is sudden increase in wavelength at pH 13.00 from 194.50 nm (pH 10.56) to 203.50
RESULTSTable 3. pH change, colour change and spectral profile
Sr. No pHchange
Colour change Spectral shift(nm)
1 1.87 Alizarin crimson 208.502 1.99 Vermilion hue 193.003 2.85 Cadmium red 193.004 4.70 Gold ochre transparent 193.505 5.25 Raw sienna 194.006 6.16 Raw sienna 194.007 7.46 Venetian red 194.008 8.47 Venetian red 194.009 10.56 Venetian red 194.5010 13.00 Cadmium orange 203.50
♦ With increase in pH there is distinct change in colour and the spectralcharacteristics of the juice
Fig 1 a. shows two peaks. Major peak at 208.5 with 3.972 absorbance and minor peak at 265.5 nm with 1.108
1b. Shows two peaks. Major peak at 193.00 nm with 2.488 absorbance and second peak at 264.00 nm with very less absorbance of 0.249
1c. Shows two peaks. Major peak at 193.00 nm with 2.408 absorbance and second peak at 262.00 nm with very less absorbance of 0.215
Fig. 1 a Fig 1 b
pH 1.87 pH 1.99
Fig 1 c
pH 2.85
Fig. 2 a Fig. 2b Fig. 2c
Fig. 2 a. shows only one prominent peak at 193.5 nm with absorbance of 2.568.
2 b & c. shows common peak at 194.00 nm with absorbances of 2.540 and 2.619 respectively.
pH 4.70 pH 5.25 pH 6.16
Fig. 3 a
Fig. 3d
Fig. 3 b Fig. 3 c
Fig. 3. (a-c) display sharp peaks with high absorbance at a very narrow range 193-194.5 nm and a spectral shift occurs at high pH (d) at 203 nm with change of the colour from venetian red to cadmium orange
pH 7.46 pH 8.47 pH 10.56
pH 13.00
DISCUSSION•Kokum juice at natural pH (1.87) does not show any absorbance between 600-700 nm. However there is a weak absorbance over a broad bandwidth of 400-600 nm which was found to diminish with higher pH.
•At the original pH there is a distinct absorption at 265 nm which diminishes in intensity with increasing pH and then disappears at pH 4.7 indicating a distinct chemical change.
•The absorbance of the solution gradually increases between 400-250 nm between 4.70-13.00 pH
DISCUSSION
• At 13.00 pH the absorption profile is very smooth probably indicating presence of single chemical component with strong absorption in the UV range at 203.50 nm.
• Initially a slight change in pH shows a UV spectral shift between 208.50-193.00 nm. The absorbance peak remains almost constant from 1.99-10.56 pH.
• Between 10.56-13.00 pH the peak is shifted again from 194.50 nm to 203.50 nm.
DISCUSSION
Potential applications of the UV absorbance capacity of the pigment :-
• The strong absorbance values ( 1.108-3.972) over 193 nm-265.5 nm range shows a UV protective function of the soluble pH sensitive pigment
• The Nucleic acids (DNA & RNA) are known to strongly absorb at 260 nm
DISCUSSIONPotential of UV protectiveaction: -• The UV protective action of the Kokum
pigment may be useful in masking theskin from DNA damaging solar radiation.
• The natural juice could be an importantresource for developing cheap, organic,eco-friendly, UV-protecting sun-screens/ointments/lotions and couldhave immense potential in cosmeticsindustry
DISCUSSION• The Chromic shift associated with pH
change could be useful property forproducing either low cost pHindicator papers (for a pH range of 3-13) or pH sensitive opto-electronicbiosensors which can be employedunder highly alkaline bioreactorconditions
• The simple Kokum juice can thus serveto be a forerunner to new products andprocesses in cosmetics and biosensorindustry