C‑8 <i>N</i>‑Ethyl-2-pyrrolidinone-Substituted Flavan-3-ols from the Leaves of <i>Camellia sinensis</i> var. <i>pubilimba</i>

<i>Camellia sinensis</i> var. <i>pubilimba</i>, one variety of the genus <i>Camellia</i> sect. <i>Thea</i> (Theaceae), has been used for producing green tea mainly by the local people of its growing areas of Guangxi province, China. Forty compounds, including eight C-8 <i>N</i>-ethyl-2-pyrrolidinone-substituted flavan-3-ols (<b>1</b>–<b>8</b>) and their substituted unit <i>N</i>-ethyl-5-hydroxy-2-pyrrolidinone (<b>9</b>), four flavan-3-ol monomers (<b>10</b>–<b>13</b>) and one dimer (<b>14</b>), nine flavonoids (<b>15</b>–<b>23</b>), three hydrolyzable tannins (<b>24</b>–<b>26</b>), two lignans (<b>27</b>–<b>28</b>), 11 simple phenolics (<b>29</b>–<b>39</b>), and caffeine (<b>40</b>), were first isolated and identified from the leaves. Their structures were determined by detailed spectroscopic analysis and comparison with the literature data and authentic samples. Both <b>1</b> and <b>4</b> were obtained as a mixture of the <i>N</i>-ethyl-2-pyrrolidinone C-5 enantiomers (<b>1a</b> and <b>1b</b> and <b>4a</b> and <b>4b</b>), respectively, while the resolution of another three pairs of enantiomers (<b>2</b> and <b>3</b>, <b>5</b> and <b>6</b>, and <b>7</b> and <b>8</b>) was achieved. Among them, <b>1b</b> is a new compound whose NMR data together with its enantiomer (<b>1a</b>) were reported for the first time, while <b>2</b> and <b>3</b> are two new natural products. Most of the isolates exhibited significant antioxidant activities, stronger than ascorbic acid and trolox, while parts of the isolates, particularly C-8 <i>N</i>-ethyl-2-pyrrolidinone-substituted flavan-3-ols, showed obvious inhibitory effects on acetylcholinesterase (AChE). The results indicated that <i>C. sinensis</i> var. <i>pubilimba</i> is a valuable plant resource for tea production

New Flavan-3-ol Dimer from Green Tea Produced from <i>Camellia taliensis</i> in the Ai-Lao Mountains of Southwest China

<i>Camellia taliensis</i> (W. W. Smith) Melchior, belonging to the genus <i>Camellia</i> sect. <i>Thea</i> (Theaceae), is an endemic species distributed from the west and southwest of Yunnan province, China, to the north of Myanmar. Known as a wild tea tree, its leaves have been used commonly for producing tea beverages by the local people of its growing area. One new flavan-3-ol dimer, talienbisflavan A (<b>1</b>), was isolated from green tea prepared from the leaves of <i>C. taliensis</i> collected from the east side of the Ai-Lao mountains, Yuanjiang county of Yunnan province, China. In addition, five hydrolyzable tannins (<b>2</b>–<b>6</b>), five flavonols and flavonol glycosides (<b>9</b>–<b>13</b>), three flavan-3-ols (<b>14</b>–<b>16</b>), nine simple phenolic compounds and glycosides (<b>7</b>, <b>8</b>, and <b>17</b>–<b>23</b>), and caffeine (<b>24</b>) were identified. Their structures were determined by detailed spectroscopic analysis. All of the isolated phenolic compounds were tested for their antioxidant activities by DPPH and ABTS⁺ radical scavenging assays. The contents of its main chemical compositions were also compared with those collected from the Lincang area of Yunnan province by high-performance liquid chromatography analysis

A new arbutin derivative from the leaves of <i>Vaccinium dunalianum</i> wight

<p>A new arbutin derivative, namely dunalianosides J (<b>1</b>), along with six known compounds, arbutin (<b>2</b>), robustaside A (<b>3</b>), 6′-<i>O</i>-caffeoylarbutin (<b>4</b>), dunalianoside D (<b>5</b>), kaempferol 3-<i>O</i>-<i>β</i>-D-glucopyranoside (<b>6</b>) and kaempferol 3-<i>O</i>-<i>β</i>-D-sambubioside (<b>7</b>) were isolated from the leaves of <i>Vaccinium dunalianum</i> Wight (Ericaceae). The structure of <b>1</b> was elucidated by extensive 1D and 2D NMR, HR-MS and CD spectroscopic analyses. In which, kaempferol 3-<i>O</i>-<i>β</i>-D-sambubioside (<b>7</b>) was isolated from the genus <i>Vaccinium</i> for the first time.</p

New cytotoxic lignan glycosides from <i>Phyllanthus glaucus</i>

<div><p>During the process of exploring bioactive lead compounds from <i>Phyllanthus</i> species, two new glycosides including an arylnaphthalene lignan, diphyllin 4-<i>O</i>-α-l-arabinopyranosyl-(1 → 3)-α-l-arabinopyranoside (<b>1</b>), and a phenolic compound, 3,4,5-trimethoxybenzyl alcohol 7-<i>O</i>-α-l-arabinofuranosyl-(1 → 6)-β-d-glucopyranoside (<b>2</b>), were isolated from the methanol extract of the whole plants of <i>Phyllanthus</i><i>glaucus</i> Wall. ex Müll. Arg. In addition, 31 known compounds, including 19 lignan derivatives (<b>3</b>–<b>21</b>), four phenylpropanoids (<b>22</b>–<b>25</b>), seven simple phenolics (<b>26</b>–<b>32</b>) and one monoterpenoid (<b>33</b>) were obtained. Their structures were determined on the basis of the HR-ESI-MS, 1D and 2D NMR spectroscopic analysis, and pre-column derivative/chiral HPLC analysis in case of <b>1</b> for the absolute configurations. All these compounds were obtained from <i>P. glaucus</i> for the first time. Moreover, the known lignan glycoside, phyllanthusmin C (<b>5</b>) showed <i>in vitro</i> cytotoxicities against HL-60, MCF-7 and SW480 cells with IC₅₀ values of 9.2 ± 0.2, 19.2 ± 1.7 and 20.5 ± 0.9, respectively.</p></div

Cytotoxic Bisbenzylisoquinoline Alkaloids from <i>Stephania epigaea</i>

Six new bisbenzylisoquinoline alkaloids (<b>1</b>–<b>6</b>) and seven known compounds (<b>8</b>–<b>14</b>) were isolated from the tubers of <i>Stephania epigaea</i>, in addition to the major alkaloid, cepharanthine (<b>7</b>). The structures of <b>1</b>–<b>6</b> were elucidated by combined spectroscopic data analysis and chemical methods, with their configurations determined from their optical rotation values and confirmed using circular dichroism. Compounds <b>1</b>–<b>6</b> belong to the oxyacanthine type of bisbenzylisoquinoline alkaloids and have a rare methylenedioxy substituent. Compound <b>1</b>, a dimer composed of benzylisoquinoline and seco-aristolactam units, represents a new type of bisbenzylisoquinoline alkaloid, while compounds <b>3</b>–<b>6</b> are bisbenzylisoquinoline <i>N</i>-oxides. These compounds were evaluated for their in vitro cytotoxicities against six human cancer cell lines (A-549, ECA109, HL-60, MCF-7, SMMC-7721, and SW480). Cepharanthine (<b>7</b>), the major component of <i>S. epigaea</i>, exhibited cytotoxicity against all of these cancer cell lines except ECA109, while its known analogue, <b>10</b>, displayed cytotoxicity against all six cancer cell lines

Methylenebisnicotiflorin: a rare methylene-bridged bisflavonoid glycoside from ripe Pu-er tea

<p>A new methylene-bridged dimeric flavonol glycoside, methylenebisnicotiflorin (<b>1</b>), was isolated from ripe Pu-er tea, along with 10 known flavonoids (<b>2</b>–<b>11</b>) and seven known phenolic compounds (<b>12</b>–<b>18</b>). The structure elucidation was based on spectroscopic analysis. Among them, 1,3-dihydroxyphenyl-2-<i>O</i>-sulfate (<b>13</b>), 2,3,4-trihydroxybenzoic acid (<b>16</b>) and 3,3′,4,4′-tetrahydroxybiphenyl (<b>18</b>) are reported from tea plants for the first time.</p

Carboxymethyl- and Carboxyl-Catechins from Ripe Pu-er Tea

Ripe Pu-er tea, a special microbial postfermented tea originated from Yunnan Province, China, since ancient times, is made from green Pu-er tea prepared from the leaves of <i>Camellia sinensis</i> var. <i>assamica</i> (Theaceae). Chemical investigation on thearubigin (<i>n</i>-BuOH-soluble) fraction of the commercial ripe Pu-er tea, led to the identification of four new flavan-3-ol derivatives, 8-carboxymethyl-(+)-catechin (<b>1</b>), 8-carboxymethyl-(+)-catechin methyl ester (<b>2</b>), 6-carboxymethyl-(+)-catechin (<b>3</b>), and 6-carboxyl-(−)-gallocatechin (<b>4</b>), together with 18 known compounds, including other three flavan-3-ol derivatives (<b>5</b>–<b>7</b>), 10 flavonoid glycosides (<b>8</b>–<b>17</b>), two hydrolyzable tannins (<b>18</b> and <b>19</b>), two quinic acid derivatives (<b>20</b>–<b>21</b>), and a purine alkaloid (<b>22</b>). Flavonoid glycosides <b>8</b>–<b>11</b> are reported from tea plants for the first time. The thearubigin fraction of ripe Pu-er tea was qualitatively analyzed by HPLC, and gallic acid was found to be the major component. Compounds <b>4</b>, <b>6</b>–<b>17</b>, <b>21</b> and <b>22</b> were tested for their acute activities on insulin sensitivity in differentiated 3T3-L1 adipocytes, but none of them showed significant bioactivity at a concentration of 10 μM

Chemical constituents from <i>Piper wallichii</i>

<div><p>Fifteen known compounds including four triterpenoids (<b>1</b>–<b>4</b>), one sterol (<b>5</b>), one diketopiperazine alkaloid (<b>6</b>) and nine phenolics (<b>7</b>–<b>15</b>) were isolated from the stems of <i>Piper wallichii</i>. Their structures were elucidated by means of spectroscopic analysis, and acidic hydrolysis in case of the 2-oxo-3β,19α,23-trihydroxyurs-12-en-28-oic acid β-D-glucopyranosyl ester (<b>1</b>). The structure of compound <b>1</b> was fully assigned by 1D and 2D NMR experiments for the first time. All isolates were tested for their antibacterial, antifungal, anti-inflammatory and antiplatelet aggregation bioactivities.</p></div

Two New Highly Oxygenated and Rearranged Limonoids from <i>Phyllanthus cochinchinensis</i>

A new 6/6/5/6-fused limonoid, phyllanthoid A (<b>1</b>), possessing both 19/30 and 19/29 oxygen bridges was isolated from <i>Phyllanthus cochinchinensis</i> (Euphorbiaceae), together with a new related limonoid, phyllanthoid B (<b>2</b>). Their structures were determined by spectroscopic analysis and single-crystal X-ray diffraction in the case of <b>1</b>. Compound <b>1</b> displayed moderate antifeedant against the generalist plant-feeding insect <i>Spodoptera exigua</i> and cytotoxicity against the MCF-7 cell line

6′-<i>O</i>-Caffeoylarbutin inhibits melanogenesis in zebrafish

<div><p>6′-<i>O</i>-Caffeoylarbutin, an arbutin derivative, is a naturally occurring glucoside of hydroquinone from <i>Vaccinium dunalianum</i>. On anti-melanogenic effect assay, 6′-<i>O</i>-caffeoylarbutin expressed a stronger anti-melanin activity in a dose-dependent manner with about a two-fold more than that of arbutin, but with less toxicity about a two-fold lower than that of arbutin. In addition, melanin synthesis could be fully recovered after the removal of 6′-<i>O</i>-caffeoylarbutin. The result suggested that 6′-<i>O</i>-caffeoylarbutin could be a candidate natural product to serve as a skin-whitening ingredient with the merits of potent melanin inhibition, less toxicity and reversible melanin synthesis after stopping use.</p></div