Chemical fingerprinting for identification/authentication of botanical materials

The identification or authentication of whole botanical materials requires a holistic approach. It is not sufficient to simply measure a marker or two. A chemical fingerprint is either the chromatographic or spectral (with no separation) pattern obtained for a solid or extract of a botanical material. Like all fingerprints, specific data points are meaningless and the whole pattern must be considered using multivariate (chemometric) methods.

Botanical identification has two requirements; the unknown sample is identified by direct comparison to an authentic botanical and a collection of authentic botanicals (inclusivity panel) is available to account for expected variation with respect to species/variety, year, location, processing, and any other appropriate variable. In general, the inclusivity panel is used to construct a model using SIMCA (soft independent modeling of class analogy) or PLS-DA (partial least squares-discriminant analysis), although there are many other techniques. Fingerprints of an unknown botanical are compared to the model and yield a binary answer, YES it is authentic, or NO, it is not authentic.

Targeted analyses are possible when there is an anticipated adulterant or substitute botanical. Otherwise the analyses are non-targeted. There are numerous advantages to targeted analyses. An appropriate analytical method can be selected and optimized and the authentic and adulterant botanicals can be tested and a model developed. Fingerprints of the authentic and adulterant botanicals can be digitally added to predict patterns for various levels of adulteration. And, the degree of adulteration can be quantified.

Non-targeted analyses proceed in a similar manner. Fingerprints for an authentic inclusivity panel are collected and a chemometric model is constructed. Since the adulterant is unknown, any botanical whose fingerprint falls outside the specified confidence limit is judged to be adulterated. However, since the adulterant is unknown, multiple analyses may be necessary for comprehensive coverage. Until the adulterant is identified, quantification is not possible.