| dc.description.abstract | Fungal melanin has several advantages such as lower cost, and easier for purification
and production at a larger scale. Thus, fungi are excellent sources of natural melanin.
Despite of having many significant bioactivities, one of the most challenging aspects
of melanins is that they are insoluble in water. Previous studies proved that in vitro
melanin modified with arginine would improve the water solubility, which could
enhance their biological activities. Therefore, the objectives of the research were to
evaluate cytotoxicity, anti-radiation activity and neuroprotective effects of argininemodified melanin prepared from Calvatia craniiformis and Xylaria sp.
Consequently, the extraction and purification procedures involved the use of alkaline
solution, then modification was the next step. Arginine modification with 1:1 mass
ratio were choosen for futher use due to the highest absorbance value and the darkest
color observation. FTIR spectra analysis were carried out to confirm product received
from modification and it was found to be a typical melanin with arginine has been
binding successfully.
In cytotoxicity activity, SRB method was used to evaluated that melanin derivatives.
At the concentration of 100 µg/mL, arginine modified melanin extracted from Calvatia
craniiformis and Xylaria sp. inhibited -2.99% and -3.16% cell growth, respectively,
which were not toxic to HepG2 cells.
In anti-radiation experiment, arginine-modified melanins displayed anti-radiation
activity in Staphylococcus aureus when the bacteria were expose to 254nm UV light
within 20 minutes. This showed melanin derivatives had biological activities in vitro
and could play as promising radiation protection agent.
Additionally, in vitro neuroprotective effects, the toxicity of H2O2 and MPTP toward
SH-SY5Y cells was proven as dependent of concentration. 1mM H2O2 and 0.5mM
could inhibit approximately 50% cellviability. Both arginine-modified C. craniiformis
and Xylaria sp. melanin (10-100 µg/mL) had no toxic to SH-SY5Y cells and they could
protect the neuroblastoma cells from H2O2 toxicity. Specifically, at the concentration
of 100 µg/mL, C. craniiformis and Xylaria sp. melanin derivatives could enhance up
to 20% cell viability of SH-SY5Y cells when treated with H2O2, which is comparable
with the positive control (20µM Resveratrol) with the viability of 35.5%. In contrast,
modified melanin of C. craniiformis at the concentration from (10-100 µg/mL) could
not protect neuron cells from damage while modified Xylaria sp. melanin could protect
human neuroblastoma cells from neurotoxin at the concentration higher than 50
µg/mL.
The results suggested arginine-modified melanin was a promising candidate agent to
treat oxidative injury of neurocytes, which is worth further investigation. | en_US |
