A New HPLC-UV Method Using Hydrolyzation with Sodium Hydroxide for Quantitation of Trans-p-Hydroxycinnamic Acid and Total Trans-p-Hydroxycinnamic Acid Esters in the Leaves of Ligustrum robustum

Abstract

Trans-p-hydroxycinnamic acid and its esters in the leaves of Ligustrum robustum might be a new resource to prevent diabetes and its complications. In the present study, a new HPLC-UV method using hydrolyzation with sodium hydroxide for quantitation of trans-p-hydroxycinnamic acid and total trans-p-hydroxycinnamic acid esters in the leaves of L. robustum was developed, since it was difficult and troublesome to analyze no less than 34 trans-p-hydroxycinnamic acid esters by usual HPLC. The extract of L. robustum was hydrolyzed with sodium hydroxide at 80 °C for 2 h, and then, hydrochloride was added. HPLC analysis was performed in reverse phase mode using a C-18 column, eluting with methanol-0.1% acetic acid aqueous solution (40:60, v/v) in isocratic mode at a flow rate of 1.0 mL·min−1 and detecting at 310 nm. The linear range for trans-p-hydroxycinnamic acid was 11.0–352.0 μg·mL−1 (r2 = 1.000). The limit of detection and limit of quantification were 2.00 and 6.07 μg·mL−1, respectively. The relative standard deviations of intra-day and inter-day variabilities for trans-p-hydroxycinnamic acid were less than 2%. The percentage recovery of trans-p-hydroxycinnamic acid was 103.3% ± 1.1%. It is the first HPLC method using hydrolyzation for quantification of many carboxylic esters. Finally, the method was used successfully to determine trans-p-hydroxycinnamic acid and total trans-p-hydroxycinnamic acid esters in various extracts of the leaves of L. robustum. The 60–70% ethanol extracts of L. robustum showed the highest contents of free trans-p-hydroxycinnamic acid (3.96–3.99 mg·g−1), and the 50–80% ethanol extracts of L. robustum displayed the highest contents of total trans-p-hydroxycinnamic acid esters (202.6–210.6 mg·g−1). The method can be applied also to the quality control of the products of L. robustum.

Monoterpenoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities (II)

“…Blume, a shrub of the Oleaceae family, is widespread in Southwest China, Vietnam, Burma, Cambodia, and India [3]. The leaves of L. robustum, containing 3.96-3.99 mg•g −1 trans-p-hydroxycinnamic acid and 202.6-210.6 mg•g −1 total transp-hydroxycinnamic acid esters [4], have been not only used as a heat-clearing and detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, anti-diabetic, and weight-reducing folk medicine [3]. In the preceding researches on L. robustum [3][4][5][6][7][8][9][10][11][12][13][14][15], about 90 chemical ingredients (of which 34 ingredients belonged to trans-p-hydroxycinnamic acid detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, antidiabetic, and weight-reducing folk medicine [3].…”

“…The leaves of L. robustum, containing 3.96-3.99 mg•g −1 trans-p-hydroxycinnamic acid and 202.6-210.6 mg•g −1 total transp-hydroxycinnamic acid esters [4], have been not only used as a heat-clearing and detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, anti-diabetic, and weight-reducing folk medicine [3]. In the preceding researches on L. robustum [3][4][5][6][7][8][9][10][11][12][13][14][15], about 90 chemical ingredients (of which 34 ingredients belonged to trans-p-hydroxycinnamic acid detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, antidiabetic, and weight-reducing folk medicine [3]. In the preceding researches on L. robustum [3][4][5][6][7][8][9][10][11][12][13][14][15], about 90 chemical ingredients (of which 34 ingredients belonged to transp-hydroxycinnamic acid esters) involving phenylmethanoid glycosides, phenylethanoid glycosides, monoterpenoid glycosides, iridoid glycosides, butenol glycosides, hexenol glycosides, lignan glycosides, flavonoid glycosides, triterpenoids, sugar esters, and other compounds were separated and elucidated.…”

“…In the preceding researches on L. robustum [3][4][5][6][7][8][9][10][11][12][13][14][15], about 90 chemical ingredients (of which 34 ingredients belonged to trans-p-hydroxycinnamic acid detoxicating functional tea (Ku-Ding-Cha) but also consumed as a hypotensive, antidiabetic, and weight-reducing folk medicine [3]. In the preceding researches on L. robustum [3][4][5][6][7][8][9][10][11][12][13][14][15], about 90 chemical ingredients (of which 34 ingredients belonged to transp-hydroxycinnamic acid esters) involving phenylmethanoid glycosides, phenylethanoid glycosides, monoterpenoid glycosides, iridoid glycosides, butenol glycosides, hexenol glycosides, lignan glycosides, flavonoid glycosides, triterpenoids, sugar esters, and other compounds were separated and elucidated. At the same time, the antioxidant capacities and inhibitory actions of FAS, α-glucosidase, and α-amylase of many constituents were reported.…”