This is in several supplements. BLR Han Swolo. Olympus Labs Ep1louge... Just to name a few.
I'm going to steal from the Evomuse Top Muscle writeup to make this easier:
Ligustrazine
Next up, we’ve got a two-pronged attack from Ligustrazine—preventing muscle atrophy and promoting muscle growth. In research, there’s a few common ways to study muscle atrophy; one of them is to “denervate” a muscle, which involves clipping off the nerve supply, so it no longer gets electrical signals. I remember doing this in college biology lab, interesting stuff. You’re pretty much guaranteed a predictable amount of atrophy. Denervated rats treated with Ligustrazine lost significantly less muscle at 7, 14, and 28 days vs. control (61). Another common and reliable way to induce atrophy is to make a muscle weightless, which is referred to as “suspension”. The Ligustrazine treated rats showed significantly less muscle loss vs. control (62).
As for the second prong, Ligustrazine increases glucose uptake in muscle cells, upregulates mitochondrial biogenesis, and significantly increases BMP-7 (which is a key player in muscle growth, see BMP write-up for more info). And for a finishing move, it is a strong ROS scavenger, reduces unwanted inflammatory cytokines, and promotes vasodilation
61. Wang H, Liang B, Peng C, Wang P. [Effect of Ligustrazine on expressions of FoXO3a, MAFbx, and MuRF1 in denervated skeletal muscle atrophy rats]. Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi Zhongguo Xiufu Chongjian Waike Zazhi Chin J Reparative Reconstr Surg. 2012 May;26(5):597–600.
62. Zhang H, He Z, Gao Y, Hinghofer-Szalkay HG, Fan X. Muscle composition after 14-day hindlimb unloading in rats: effects of two herbal compounds. Aviat Space Environ Med. 2007 Oct;78(10):926–31.
63. Gao X, Zhao X, Zhu Y, Li X, Xu Q, Lin H, et al. Tetramethylpyrazine protects palmitate-induced oxidative damage and mitochondrial dysfunction in C2C12 myotubes. Life Sci. 2011 Apr 25;88(17–18):803–9.
64. Yuan X, Liu L, Fu Q, Wang C. Effects of ligustrazine on ureteral obstruction-induced renal tubulointerstitial fibrosis. Phytother Res PTR. 2012 May;26(5):697–703.