Fuzhuanins A and B: The B‑ring Fission Lactones of Flavan-3-ols from Fuzhuan Brick-Tea

Fuzhuan brick-tea is a special dark tea prepared from the leaves of <i>Camellia sinensis</i> var. <i>sinensis</i>. Its production involves a fungal fermentation stage, which forms the unique flavors and functions by a series of biochemical reactions. Our phytochemical research of the material led to the isolation of two new B-ring fission lactones of flavan-3-ols, fuzhuanins A (<b>1</b>) and B (<b>2</b>). In addition, three other flavan-3-ol derivatives (<b>3</b>–<b>5</b>), three flavone <i>C</i>-glycosides (<b>6</b>–<b>8</b>), eight flavonoid <i>O</i>-glycosides (<b>10</b>–<b>17</b>), five simple phenolics (<b>19</b>–<b>23</b>), two norisoprenoid glycosides (<b>24</b>, <b>25</b>), two sesquiterpenoids (<b>26</b>, <b>27</b>), and theobromine (<b>28</b>), as well as two flavonoid anions (<b>9</b> and <b>18</b>), were also identified. The structures of these compounds were determined by spectroscopic methods. Compounds <b>4</b>, <b>19</b>, <b>20</b>, <b>22</b>–<b>24</b>, <b>26</b>, and <b>27</b> were reported for the first time in <i>Camellia</i> spp. and tea. Furthermore, HPLC analysis method was performed to compare the chemical constituents of the before/after fungal fermentation Fuzhuan brick-teas. Compound <b>1</b> was indicated as one of the major characteristic constituents generated in the fungal fermentation process. The IC₅₀ value of the antiproliferative activity of <b>2</b> on HeLa cells was assayed as 4.48 μM. None of the isolated compounds showed any inhibition activity against the enteric pathogenic microbes at 800 μg/mL by the hole plate diffusion method