Liquid Chromatography - Tandem Mass Spectrometry Discovery and Profiling of Anthocyanin Flavonoids in Cannabis

Most people are familiar with the main bioactive metabolites in Cannabis – cannabinoids and terpenes.  The profile of each can be quite complex both in terms of numbers of different species, but also their abundance.  In a similar fashion, varying types and abundances of flavonoid compounds also contribute to the complex chemotype of a Cannabis flower.  Flavonoids are polyphenolic compounds that confer antioxidant capacity.  Anthocyanins are a type of flavonoid that also confer colors, such as red, yellow, blue, and purple to a plant.  To date, these have not been comprehensively profiled in Cannabis, despite clearly wide variations in plant colorations.  In this work, we developed a liquid chromatography – triple quadrupole – mass spectrometry (LC-MS) method to target and identify anthocyanins in a series of low-THC Cannabis samples, or hemp.  Anthocyanins can yield rich chemical fragmentation patterns in a mass spectrometer that can be used for identification of species.  Initially, we started with a precursor ion scan approach to identifying anthocyanins.  Identified species were ultimately targeted using highly sensitive and specific multiple reaction mode transitions.  The differences among anthocyanin profiles from different plant genetics is remarkable.  Each plant appears to have its own unique fingerprint of 5 – 10 major anthocyanins.  Further, these anthocyanin profiles can be modulated based on lighting conditions during cannabis growth.  The controlled deliverance of distinct photoperiods using white in combinations with additional red LED lighting created marked changes in anthocyanin profiles, as well as terpene and cannabinoid profiles.  The hemp color palate is indeed rich, and like other bioactive metabolites, can be altered through judicious choice of growth conditions.

Learning Objectives:

1.    Explain the role and use of liquid chromatography – tandem mass spectrometry for cannabis analysis.

2.    Describe anthocyanin flavonoid compounds and their role in providing color to cannabis plants.