From Microcystin-LR to the full set of nine variants—Weiyel's mixed standards have arrived.

Microcystins (MCs) are secondary metabolites produced by toxic cyanobacteria such as *Microcystis*, *Anabaena*, and *Oscillatoria*; chemically, they are cyclic heptapeptides formed by the condensation of seven amino acids. Structurally, variation occurs at only two positions; substituting an amino acid at one of these sites yields a new toxin variant. In essence, these nine toxins are like siblings in a family—sharing a similar appearance but employing identical mechanisms of harm. Upon entering hepatocytes, they disrupt the cytoskeleton and cause hepatic hemorrhage and necrosis, while also promoting tumor growth. Among them, MC-LR is the most potent and prevalent; it is classified by the World Health Organization (WHO) as a Group 2B "possibly carcinogenic" agent. Due to the availability of the most comprehensive toxicity data, MC-LR is currently the only variant subject to mandatory regulatory limits, while the other eight are primarily used for risk assessment and total load calculations.

Weiye has developed corresponding certified reference materials for detection—available now!

Product details are as follows: