International Journal of Noni Research - Noni Family

N. Mathivanan et al. Chemical and biological properties of Morinda spp.
distilled water (3.9 ml), and kept in screw cap containers under dark conditions
at 40 o . To 0.1 ml of this solution, 9.7 ml of 75% ethanol and 0.1 ml of 30%
ammonium thiocyanate were added. After 3 min, 0.1 ml of ferrous chloride in
3.5% HCl was added to the reaction mixture and the absorbance of the red
color was measured at 500 nm every 24 h, until one day after absorbance of
the control reached maximum. The control and standard were subjected to the
same procedure as the sample except for the control, where there was no
addition of sample, and for the standard 4 mg of sample were replaced with
4 mg of a-tocopherol or BHT.
Thiobarbituric acid (TBA) test
The same samples as prepared for the FTC method were used in TBA test. To
1 ml of sample solution, 2 ml each of 20% aqueous trichloroacetic acid and
aqueous thiobarbituric acid were added. This mixture was then incubated in
a boiling water bath for 10 min. After cooling, it was centrifuged at 3000 rpm
for 20 min and the absorbance of supernatant was measured at 532 nm.
Antioxidative activity was recorded based on absorbance on the final day.
Antimicrobial activity
The antimicrobial activity of Morinda spp. was studied using disc diffusion
method for bacterial pathogens. In the case of phytopathogenic fungi, the fresh
and dry weights were estimated.
Determination of minimum inhibitory concentration (MIC)
Among different solvent extracts, the chloroform fruit extract was used to
determine the minimum inhibitory concentration (MIC) against different human
and plant pathogens by broth dilution assay of Hammer et al. (1996) with some
modifications. The nutrient broth (NB) and potato dextrose broth (PDB) were
used instead of heart infusion agar and Mueller Hinton Broth (MHB) with
chloroform fruit extract at the concentrations of 10–1000 mg/ml. The pathogens
were inoculated separately and the flasks were incubated at 28 ± 2°C under
shaken condition. The growth of human pathogens and mycelial weight of the
plant pathogens were measured after 24 h and 5 days, respectively. Based on
the growth, the MIC for each pathogen was determined.
Effect of fruit extracts of Morinda spp. on respiration
The effect of fruit extract of Morinda spp. on respiration in different test
organisms was determined using dark type polarographic oxygen probe. About
5 ml of distilled water was placed in the sample chamber and temperature
controlled water circulator was used in the sample chamber to maintain 30°C.
The oxygen probe was inserted into the chamber without any air bubble
between the probe tip and the water surface. Magnetic stirrer was turned on
Intl. J. Noni Res. 2007, 2(1-2) 64