350
I-type and chrysophanol-type while chrysophanol-type is also found in the leaces of
aloe (Dagne et al. 2000). Anthraquinones such as aloe emodin and aloin exhibit
strong anti oxidant activities probably due to their ability to scavenge free radicals
and also inhibit peroxidation of lipids.
In the study, the antioxidant activity of anthraquinones, anthrones, aloe emodin,
rhein amodin have been studied using a linoleic acid system. Thiocyanate method
was used to determine the degree of peroxidation inhibition of the linoleic acid
system at 37 °C. Anthrones and alzirin were identified to show the strongest antioxidant potential with no significant difference between them. Their scavenging power
was found to be even stronger than α-tocopherol and BHT while anthraquinone had
antioxidant potential stronger than rhein emodin but lesser than α-tocopherol. It was
also determined that anthrone and alzinrin’s antioxidant activity is due to their
strong reducing powers and their reducing potential increases with their concentrations. The other anthraquinones did not show any reducing activity in the experiment. Similarly in the same study the scavenging activity of anthrones and
anthraquinones was determined on the hydroxyl radicals with the result that emodin
exhibits strong scavenging potential at a concentration of 0.25 mg/ml while chrysophanol, anthraquinone, rhein and alizarin at the same dose increase the formation of
such radicals. Anthrone and aloe emodin also exhibit scavenging potential but their
capacity is lesser than that of emodin at the same concentration (Yen et al. 2000).
In another study, aloin and aloe emodin were studied for their pro-oxidant and
antioxidant activities at different doses. Radicals scavenging properties were determined using Chemiluminescence assay. Epigallocatechin-3-gallate (EGCG) was
used as a comparative antioxidant agent. The experiment established that both aloin
and aloe emodin showed antioxidant potential which increased by increasing their
dose however it was less than that of EGCG at all concentrations and aloe emodin
showed scavenging activity lesser than that of both aloin and EGCG at all concentrations. It was also found that aloin had a greater reducing tendency than aloe emodin
at all concentrations attributing it’s antioxidant potential to its reducing capacity. Also
at high doses of 1.25–2.5 mM aloin prevented DNA breakage due to OH radicals by
5–30% over the control value but increases DNA damage at lower concentrations of
300–8 μM. Both aloe emodin and EGCG at high concentrations show pro-oxidant
effects. The experiments established that the different effects of both aloin and aloe
emodin on DNA may be attributed to the difference in their structures and concentration dependencies (Tian and Hua 2005). Studies have established that several antioxidant agents can become pro-oxidants at different concentrations and therefore their
right doses should be established before their clinical use (Lee and Park 2003).
18.3.2 Bianthraquinoids
Genus does not contain many dimers however elgonica-dimers A and B
(Elgonicardine) are found in Aloe elgonica while Aloe saponaria contains
Asphodelin, Bianthracene II, III and IV in the plant’s rhizomes and roots.
C. Egbuna et al.
I-type and chrysophanol-type while chrysophanol-type is also found in the leaces of
aloe (Dagne et al. 2000). Anthraquinones such as aloe emodin and aloin exhibit
strong anti oxidant activities probably due to their ability to scavenge free radicals
and also inhibit peroxidation of lipids.
In the study, the antioxidant activity of anthraquinones, anthrones, aloe emodin,
rhein amodin have been studied using a linoleic acid system. Thiocyanate method
was used to determine the degree of peroxidation inhibition of the linoleic acid
system at 37 °C. Anthrones and alzirin were identified to show the strongest antioxidant potential with no significant difference between them. Their scavenging power
was found to be even stronger than α-tocopherol and BHT while anthraquinone had
antioxidant potential stronger than rhein emodin but lesser than α-tocopherol. It was
also determined that anthrone and alzinrin’s antioxidant activity is due to their
strong reducing powers and their reducing potential increases with their concentrations. The other anthraquinones did not show any reducing activity in the experiment. Similarly in the same study the scavenging activity of anthrones and
anthraquinones was determined on the hydroxyl radicals with the result that emodin
exhibits strong scavenging potential at a concentration of 0.25 mg/ml while chrysophanol, anthraquinone, rhein and alizarin at the same dose increase the formation of
such radicals. Anthrone and aloe emodin also exhibit scavenging potential but their
capacity is lesser than that of emodin at the same concentration (Yen et al. 2000).
In another study, aloin and aloe emodin were studied for their pro-oxidant and
antioxidant activities at different doses. Radicals scavenging properties were determined using Chemiluminescence assay. Epigallocatechin-3-gallate (EGCG) was
used as a comparative antioxidant agent. The experiment established that both aloin
and aloe emodin showed antioxidant potential which increased by increasing their
dose however it was less than that of EGCG at all concentrations and aloe emodin
showed scavenging activity lesser than that of both aloin and EGCG at all concentrations. It was also found that aloin had a greater reducing tendency than aloe emodin
at all concentrations attributing it’s antioxidant potential to its reducing capacity. Also
at high doses of 1.25–2.5 mM aloin prevented DNA breakage due to OH radicals by
5–30% over the control value but increases DNA damage at lower concentrations of
300–8 μM. Both aloe emodin and EGCG at high concentrations show pro-oxidant
effects. The experiments established that the different effects of both aloin and aloe
emodin on DNA may be attributed to the difference in their structures and concentration dependencies (Tian and Hua 2005). Studies have established that several antioxidant agents can become pro-oxidants at different concentrations and therefore their
right doses should be established before their clinical use (Lee and Park 2003).
18.3.2 Bianthraquinoids
Genus does not contain many dimers however elgonica-dimers A and B
(Elgonicardine) are found in Aloe elgonica while Aloe saponaria contains
Asphodelin, Bianthracene II, III and IV in the plant’s rhizomes and roots.
C. Egbuna et al.