Citation
Mustafa, Roheeyati Ashikin
(2009)
Antioxidant Activity And Bioactive Compounds Of Selected Tropical Plants.
Masters thesis, Universiti Putra Malaysia.
Abstract
Antioxidant does not only prevent food containing lipid and oils from
becoming rancid, but it also provides protection against harmful free radical
and has been strongly associated with reduced risk of chronic diseases such
as cardiovascular diseases, cancer and diabetes. The antioxidant activity of
21 selected tropical plant extracts was evaluated utilizing four different
assays including conjugated diene, scavenging DPPH radical, TBA and
chelating effect on ferrous ion. Bioactive compounds (total phenolics,
flavonoids, β-carotene, lycopene, α-tocopherol and ascorbic acid) were also
determined in the plants extracts. Results of the study showed that
C.caudatus extract was highly effective in the prevention of conjugated
diene formation and scavenging effect on DPPH radicals. On the other hand,
C.asiatica and P.tetragonolobus extracts demonstrated excellent activity in inhibiting malondialdehyde (MDA) formation and chelating ability on
ferrous ion. As expected, increasing the concentration of extracts used
increased the antioxidant activity in all plants tested. The antioxidant
activities of some of these plants were found to be as good as that of α-
tocopherol and BHA (Butylated hydroxyanisole). Results of the study
revealed that L.inermis extracts consisted of the highest content of phenols
and then flavonoids (catechin, epicatechin and naringenin) compared to all
the plants tested. On the other hand, excellent concentration of quercetin and
ascorbic acid were identified in V.negundo extract whilst surprisingly,
P.bleo extract showed high content of lycopene and α-tocopherol. Highest
kaempferol and myricetin was found in S.grandiflora and C.asiatica
extracts whilst luteolin and apigenin were predominantly found in
P.cordifolia and K.galanga extracts. On the other hand, highest β-carotene
content was found in G.procumbens extract. Excellent correlation
(R2=0.8613) was found between radical scavenging activity and the total
content of phenolic compounds. Similar correlation (R2=0.8430) was seen
between radical scavenging activity and flavonoids compounds. The study
suggested that phenolic compounds in particular, the flavonoids contribute
to the antioxidant activity.
Keywords: Antioxidant activity; tropical plants; bioactive compounds;
phenolic compounds; ascorbic acid.
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