Antioxidant activity
Based on the applied CK, the antioxidant potential for individual plant parts during tissue culture and acclimatization were
determined (Table 1). The underground parts had better antioxidant activity among the tissue culture regenerants while aerial
parts yielded better antioxidant activity during acclimatization in
all experimental variants. Duringtissue culture, the ORACwas highestwith mTRtreatment(927 mol g−1 TE)inthe underground parts
while the aerial part of BA-treated cultures had the least activity
(223 mol g−1 TE). On the other hand, CK-free and 2iP treatments
had the highest (433 mol g−1 TE) and lowest (47 mol g−1 TE)
ORAC after acclimatization, respectively.
Generally, there was a significant difference between tissue culture and acclimatized plantlets whensimilarplantparts ofthe same
treatment were compared. In the underground parts, there was
a marked decrease in ORAC, for instance, an 8-fold decrease was
detected in 2iP treatment after acclimatization (stage). In addition,
BA-treated plantlets showed the least decrease (2-fold) in ORAC
while the control plantlets had a 7-fold decline and the topolin
(mT, mTRand MemTTHP) treatments were lower by approximately
5–6-fold. Conversely, the general increase in ORAC in aerial parts
after acclimatization was less pronounced as the highest increase
(approximately 2-fold) was obtained in BA treatment.
Phenolic acid content
Different levels of three hydroxybenzoic derivatives namely
protocatechuic acid, 4-hydroxybenzoic acid and vanillic acid were
quantified (Fig. 1). Protocatechuic and 4-hydroxybenzoic acids
were more abundant in underground part of the tissue cultured
plantlets with the exception of the BA treatment where the aerial
part yielded higher levels. Aerial parts (with the exception of
BA-treated plantlets) generally showed an increase in levels of
protocatechuic acid after the plants were acclimatized (Fig. 1A
and B). Following acclimatization, 2iP-treated plantlets had highest level ofprotocatechuic acid whereas mTR-treated ones had the
least. The highest concentration of 4-hydroxybenzoic acids were
detected in BA regenerants among the aerial parts (Fig. 1C) and
2iP-treated for the underground parts (Fig. 1D). Vanillic acid was
only detected in the underground parts of both tissue culture and
acclimatized plantlets (Fig. 1E). The accumulation of vanillic acid
was significantly enhanced in the presence of BA. For example, in
the underground parts oftissue culture plantlets, there was approximately 57-fold increase in BA-treated plantlets when compared to
the CK-free plants. In addition, among all the phenolic acids quantified in the current study, the quantity ofvanillic acid (24.9 gg−1)
in BA-treated plantlet was the most abundant. Even afteracclimatization, BA-treated plantlets maintained a significantly higher level
of vanillic acid in the underground parts compared to other CK
treatments.
The effect of the CK treatments on the biosynthesis/accumulation of the hydroxycinnamic acid derivatives
(p-coumaric acid, caffeic acid and ferulic acid) was quantified
(Fig. 2). In the aerial part, the plantlets generally accumulated
more p-coumaric acid during tissue culture than at the acclimatization stage (Fig. 2A and B). Furthermore, the topolins (mTR and
MemTTHP) favoured p-coumaric acid accumulation as demonstrated in mTR treatment that was 7-fold more than the control.
For the underground part however, the acclimatized plantlets had
higheramounts ofp-coumaric acid when compared to similarparts
in tissue cultured plantlets. The highest amount of p-coumaric was
detected in plantlets treated with 2iP while mT-treated plantlets
had the lowest level. In terms of the ferulic acid content, mTR
Antioxidant activityBased on the applied CK, the antioxidant potential for individual plant parts during tissue culture and acclimatization weredetermined (Table 1). The underground parts had better antioxidant activity among the tissue culture regenerants while aerialparts yielded better antioxidant activity during acclimatization inall experimental variants. Duringtissue culture, the ORACwas highestwith mTRtreatment(927 mol g−1 TE)inthe underground partswhile the aerial part of BA-treated cultures had the least activity(223 mol g−1 TE). On the other hand, CK-free and 2iP treatmentshad the highest (433 mol g−1 TE) and lowest (47 mol g−1 TE)ORAC after acclimatization, respectively.Generally, there was a significant difference between tissue culture and acclimatized plantlets whensimilarplantparts ofthe sametreatment were compared. In the underground parts, there wasa marked decrease in ORAC, for instance, an 8-fold decrease wasdetected in 2iP treatment after acclimatization (stage). In addition,BA-treated plantlets showed the least decrease (2-fold) in ORACwhile the control plantlets had a 7-fold decline and the topolin(mT, mTRand MemTTHP) treatments were lower by approximately5–6-fold. Conversely, the general increase in ORAC in aerial partsafter acclimatization was less pronounced as the highest increase(approximately 2-fold) was obtained in BA treatment.Phenolic acid contentDifferent levels of three hydroxybenzoic derivatives namelyprotocatechuic acid, 4-hydroxybenzoic acid and vanillic acid werequantified (Fig. 1). Protocatechuic and 4-hydroxybenzoic acidswere more abundant in underground part of the tissue culturedplantlets with the exception of the BA treatment where the aerialpart yielded higher levels. Aerial parts (with the exception ofBA-treated plantlets) generally showed an increase in levels ofprotocatechuic acid after the plants were acclimatized (Fig. 1Aand B). Following acclimatization, 2iP-treated plantlets had highest level ofprotocatechuic acid whereas mTR-treated ones had theleast. The highest concentration of 4-hydroxybenzoic acids weredetected in BA regenerants among the aerial parts (Fig. 1C) and2iP-treated for the underground parts (Fig. 1D). Vanillic acid wasonly detected in the underground parts of both tissue culture andacclimatized plantlets (Fig. 1E). The accumulation of vanillic acidwas significantly enhanced in the presence of BA. For example, inthe underground parts oftissue culture plantlets, there was approximately 57-fold increase in BA-treated plantlets when compared tothe CK-free plants. In addition, among all the phenolic acids quantified in the current study, the quantity ofvanillic acid (24.9 gg−1)in BA-treated plantlet was the most abundant. Even afteracclimatization, BA-treated plantlets maintained a significantly higher levelof vanillic acid in the underground parts compared to other CKtreatments.The effect of the CK treatments on the biosynthesis/accumulation of the hydroxycinnamic acid derivatives(p-coumaric acid, caffeic acid and ferulic acid) was quantified(Fig. 2). In the aerial part, the plantlets generally accumulatedmore p-coumaric acid during tissue culture than at the acclimatization stage (Fig. 2A and B). Furthermore, the topolins (mTR andMemTTHP) favoured p-coumaric acid accumulation as demonstrated in mTR treatment that was 7-fold more than the control.For the underground part however, the acclimatized plantlets hadhigheramounts ofp-coumaric acid when compared to similarpartsin tissue cultured plantlets. The highest amount of p-coumaric wasdetected in plantlets treated with 2iP while mT-treated plantletshad the lowest level. In terms of the ferulic acid content, mTR
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