Organic acids, flavonoids, iridoids, and saponins were among the compounds discovered, with significant α-glucosidase inhibitory behavior in vitro that was inconsistent with substance content level.
New research in the Journal of Chromatography A has examined the flowers and stems of honeysuckle, purchased from several Chinese pharmacies, to evaluate the genus’s bioactive components among some 200 active ingredients known to have antibacterial, anti-inflammatory, antioxidant, and antiviral effects (1).
The study out of Hangzhou Normal University in Hangzhou, China found 57 compounds of interest across 34 samples drawn from different species of honeysuckle, known in China by the names Jinyinhua, Rendongteng, and Shanyinhua (1). To efficiently categorize the 57 identified ingredients, the researchers deployed two-dimensional liquid chromatography coupled to ion mobility quadrupole time-of-flight mass spectrometry (2D-LC–IM–QTOF-MS), seeking to improve upon previous detection methods including high performance liquid chromatography and gas chromatography (HPLC and GC, respectively), both coupled to and without MS, inductively coupled plasma-mass spectrometry (ICP-MS), and capillary electrophoresis (CE).
Honeysuckle, the flower of Lonicera japonica in the family Lonicerae, is reported by the researchers to have medicinal benefits including as a treatment for symptoms as common as sore throat or fever, or potentially complex as diabetes and neurodegenerative diseases, with “consistent” pharmacological efficiency (1). But as the study explains, each of the abovementioned methods used in prior experimentation offers limited peak capacity and insufficient accuracy for the desired quantification of honeysuckle compounds.
In this instance, then, ion mobility mass spectrometry (IM–MS) was chosen by the researchers for its promise in complex compound identification and analysis in natural products, also shortening analysis time, improving peak capacity and signal-to-noise ratio, and increasing sample throughput. In conjunction, time-of-flight mass spectrometry (TOF-MS) has been used in previous studies to successfully identify and quickly analyze metabolites within more than 50 batches of honeysuckle (1).
Two-dimensional liquid chromatography (2D-LC), meanwhile, was seen by the researchers as desirable over one-dimensional LC for reasons mostly already mentioned: superior resolution, peak capacity, sensitivity, and efficiency, not to mention 2D-LC’s proven use in the analysis of complex substances in nature including herbs and traditional Chinese medicine (1).
The study found that 2D-LC was able to successfully analyze, as previously stated, 34 species of honeysuckle, with 57 compounds within those samples identified by IM–MS. Those included, according to the researchers, organic acids, flavonoids, iridoids, and saponins (1). Particular attention was given to the exoenzyme alpha-glucosidase (α-glucosidase) and its inhibitory effects on enzyme activity, which the team dubbed “significant” with the lowest half maximal inhibitory concentration (IC50) value at 0.37 mg/mL, although levels varied depending on where a particular honeysuckle sample had been purchased.
Primarily for this reason, the authors concluded that evaluating content detection along with activity inhibition provides the most comprehensive picture of drug quality, since α-glucosidase inhibition in vitro was overall potent even though its levels were inconsistent from sample to sample.
(1) Shi, Y.; Jin, H.-F.; Jiao, Y.-H.; Fei, T.-H.; Liu, F.-.M.; Cao, J. Enzyme activity- and chemometrics-assisted comprehensive two-dimensional liquid chromatography coupled with ion mobility quadrupole time-of-flight mass spectrometry for the analysis of honeysuckle. J. Chromatogr. A 2023, 1702, 464090. DOI: 10.1016/j.chroma.2023.464090