Inhibition of Free Radical Degradation in Medical Grade Hyaluronic Acid - Hyaluronic Acid for Biomedical and Pharmaceutical Applications - page 113

Applying acetic acid (pH 4) as a solvent of GSH instead of saline led
to a more intensive degradation of HA. To inhibit HA degradation,
it was necessary to apply GSH in a 5-fold higher concentration
(1,000 mM) compared to the experiments in which saline was used.
A somewhat less protective effect of GSH against · OH radicals
was observed at 100 mM concentration. No protective effects of
GSH were demonstrated at low concentrations, i.e., 10 and 1 mM
( Figure 5.5 , panel A) as shown by the decrease of h values by 5.36
and 5.87 mPa.s, respectively.

5 A

B

5

8 8

4

4

6 6

3

0 0

2

4 4 3

2

1

1

2

2

0 60 180

Time [min]

120 240 300 0 60 180

Time [min]

120 240 300

Figure 5.5 Effect of 0.5% acetic acid itself (1) and the effect
of GSH dissolved in acetic acid (0.5%) on the hyaluronan
degradation induced by WBOS (0). GSH and acetic acid were
added to the reaction system before initiating the degradation of
HA (panel A) or after 1 h (panel B). The concentrations of GSH in
µM: (2) 1; (3) 10; (4) 100; and (5) 1,000

5.4 Conclusions

The use of GSH as a free radical scavenger is well-established.
However, our investigation showed that, at low pH value (e.g.,