Hydroxybenzoic Acids Are Significant Contributors to the Antioxidant Effect of Borututu Bark, Cochlospermum angolensis Welw. ex Oliv

Abstract

Borututu (Cochlospermum angolensis) is an African tree whose bark has recently emerged as a herbal dietary supplement with claims for antioxidant activity. In order to substantiate the claimed activity of borututu supplements, we performed an activity-guided fractionation of the total extract utilizing a 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay. Subsequent flash and centrifugal chromatography resulted in the isolation of gallic acid (1) and protocatechuic acid (2) as the main antioxidant constituents. Two apocarotenoids and one flavonoid were also isolated from the chloroform fraction and were identified as cochloxanthin (3), dihydrocochloxanthin (4), and 7,4′-dimethyltaxifolin (5), respectively. A High-performance liquid chromatography (HPLC) method was also developed for fingerprinting borututu samples, with Compounds 1–4 suggested as chemical markers for quality control purposes.

Pressurized Liquid Extraction for the Production of Extracts with Antioxidant Activity from Borututu (Cochlospermum angolense Welw.)

“…The presence of ellagic acid, methyl ellagic acid and their glycosides (mainly hexosides and pentosides) as representative compounds of borututu root extracts has been previously reported [ 11 , 15 ]. Ferreres et al [ 11 ] did not find protocatechuic acid in the extract obtained by infusion with water, as opposed to what has been described in the present and other studies [ 8 , 15 ]. Moreover, the presence of rhamnose and galloyl residues in the ellagic and methyl ellagic acid glycosides has been identified for the first time in this study in borututu extracts.…”

“…Moreover, the presence of rhamnose and galloyl residues in the ellagic and methyl ellagic acid glycosides has been identified for the first time in this study in borututu extracts. Regarding gallic acid, in addition to the presence of galloyl forms, this compound was also found in its free form in the present study ( Table 3 ), which agrees with the findings of Abourashed and Fu [ 8 ], whereas Pereira et al [ 15 ] found this compound attached to the flavanol gallocatechin, thus forming gallocatechin gallate in borututu extracts.…”

“…Ferreres et al [ 11 ] associated the antioxidant activity of a borututu extract with the content of ellagic acid and its derivatives. Abourashed and Fu [ 8 ] determined by DPPH assay the antioxidant activity of a methanolic extract from borututu and the fractions obtained by fractionation with different organic solvents. The authors concluded that the highest antioxidant activity observed was produced by gallic and protocatechuic acid, which were isolated with high purity.…”

“…The infusion obtained from borututu roots by decoction with water has been traditionally consumed by many African communities for the treatment of malaria and due to its hepatoprotective properties [ 5 , 6 ]. Borututu has been described as a promising source of bioactive compounds, such as mono- and sesquiterpenes [ 7 ], apocarotenoids [ 8 ] and phenolic compounds, with the latter group of compounds being related to the majority of bioactive effects of this plant.…”