HPLC (280 nm) analysis of HPCE and its different fractions.

<p>A: HPCE; B: The fraction eluted with 40% methanol, F5; C: The fraction eluted with 50% methanol, F6; D: The fraction eluted with 60% methanol, F7; E: The fraction eluted with 100% methanol, F8.</p

Identification of Proanthocyanidins from Litchi (<i>Litchi chinensis Sonn</i>.) Pulp by LC-ESI-Q-TOF-MS and Their Antioxidant Activity

<div><p>Content of total proanthocyanidins as well as total phenolics, flavonoids, antioxidant activities were evaluated for litchi (<i>Litchi chinensis</i> Sonn.) pulp of 32 cultivars. One cultivar, Hemaoli, showed the highest total proanthocyanidins and total phenolics, and DPPH or ABTS radical scavenging activities. ESI-MS and NMR analysis of the Hemaoli pulp crude extracts (HPCE) showed that procyandins composed of (<i>epi</i>)catechin unites with degree of polymerization (DP) of 2–6 were dominant proanthocyanidins in HPCE. After the HPCE was fractionated by a Sephadex LH-20 column, 32 procyanidins were identified by LC-ESI-Q-TOF-MS in litchi pulp for the first time. Quantification of individual procyanidin in HPCE indicated that epicatechin, procyanidin B2, procyanidin C1 and A-type procyanidin trimer were the main procyanidins. The radical scavenging activities of different fractions of HPCE as well as six procyanidins standards were evaluated by both DPPH and ABTS assays. HPCE fractions showed similar antioxidant activities with those of Vc and six individual procyanidins, the IC₅₀ of which ranged from 1.88 ± 0.01 to 2.82 ± 0.10 μg/ml for DPPH assay, and from 1.52 ± 0.17 to 2.71 ± 0.15 μg/ml for ABTS assay. Such results indicate that litchi cultivars rich in proanthocyanidins are good resources of dietary antioxidants and have the potential to contribute to human health.</p></div

Direct infusion ESI-MS spectrum of Hemaoli pulp crude extracts (HPCE) in the negative mode.

<p>Direct infusion ESI-MS spectrum of Hemaoli pulp crude extracts (HPCE) in the negative mode.</p

Tentative identification and quantification of procyanidins in HPCE by using LC-ESI-MS.

<p>N.D.: Not detected</p><p>Compound 1, 2, 4 and 30 were further identified according to the chemical standards. Individual procyanidins were calculated as mg procyanidin B2 equivalent (mg PB2E/100 g DW).</p><p>Tentative identification and quantification of procyanidins in HPCE by using LC-ESI-MS.</p

Antioxidant activity of HPCE, fractions, and procyanidins standards by DPPH (A, B) and ABTS (C, D) assays.

<p>EP stands for (–)-epicatechin, and PA1, PA2, PB1, PB2, PC1 stand for the standards of procyanidin A1, A2, B1, B2, and C1, respectively.</p

¹³C NMR spectrum of HPCE.

<p>Samples were dissolved in CD₃OD.</p

Contents of total phenolics, total flavonoids, total proanthocyanidins, and antioxidant activities of pulp extracts of 32 litchi cultivars.

<p>Data were presented as the mean ± S.D. (n = 3) on a dry weight (DW). Total phenolics were calculated as mg gallic acid equivalent (mg GAE/g DW). Total flavonoids were calculated as mg catechin equivalent (mg CE/g DW). Total procyanidins were calculated as mg procyanidin B2 equivalent (mg PB2E/g DW). The scavenging of DPPH and ABTS radicals were calculated as μg vitamin C equivalent (μg VcE/g DW), respectively.</p><p>Contents of total phenolics, total flavonoids, total proanthocyanidins, and antioxidant activities of pulp extracts of 32 litchi cultivars.</p