There is a very interesting alkaloid called theacrine, closely related to caffeine, with a range of beneficial effects, and contained in large quantities in a variety of tea called C. assamica var. kucha. There's not much info available online on this variety, but apparently it grows naturally in Meng Song. It is supposed to be very bitter. Look at this interesting blog post by Zhi Zheng:http://www.zhizhengtea.com/puerblog/men ... itter-tea/
I also found this study, which states that theacrine has been found to be a minor component of C. sinensis, too:http://www.o-cha.net/english/conference ... B-P-78.pdf
Now I'm thinking, could this not be what gives some teas from Bulang Shan that special bitterness? I've always wondered why the bitterness of those teas was so, not just strong, but different. I have also heard Lao Man E tea referred to as "kucha".
What do you think about this? Does tea from any other mountains have this kind of bitterness?