Over Half the Polyphenols in Moroccan Zantaz Honey Are One Compound

• Methyl syringate averaged 340 mg/kg and made up 54% to 58% of total polyphenols in five of six samples, and 40% in the sixth. Epicatechin (77 mg/kg), syringic acid and catechin were the next most abundant.
• Pollen counts confirmed Bupleurum spinosum as the leading nectar source in all six honeys, at 51% to 80% of grains.
• In cell cultures, all six honeys showed antioxidant activity (0.3 to 1.2 quercetin equivalents) and slowed leukaemia cell growth. The concentration needed to halve growth ranged from 31 to 46 mg/mL.
• Across the six samples, both activities correlated most closely with methyl syringate and gallic acid. This is a correlation, not proven cause.
• Diastase activity averaged 22 shade units against a required minimum of 8, and sucrose was at trace levels.

In five of six Zantaz honeys, a single compound called methyl syringate made up between 54% and 58% of all polyphenols. Honeys from robinia, rape, chestnut, clover and several other plants have been reported to contain only 0.09 to 5.04 mg/kg of it, while these six averaged 340 mg/kg. A preliminary in vitro study of Zantaz honey, which bees make from the nectar of the Atlas Mountain shrub Bupleurum spinosum, found that this profile came with antioxidant and antiproliferative activity in cultured human cells, and that the activity tracked methyl syringate and gallic acid.

The researchers bought six honeys from beekeepers in the Fez and Taza regions of Morocco and confirmed by pollen counts that Bupleurum spinosum was the leading source, at 51% to 80% of grains. Chromatography identified 19 polyphenols. Human leukaemia cells were then exposed to the honey for up to 72 hours, and a separate colon cell line measured antioxidant activity. Honey interferes with the standard cell viability reading, so the team ran honey only controls and subtracted that interference from the results.

The cell results followed the chemistry. The honey concentration needed to halve leukaemia cell proliferation ranged from 31 mg/mL in the most active sample to 46 mg/mL in the least active. That weakest sample also had the lowest methyl syringate share, 40%, and low amounts of gallic acid. Antioxidant activity varied more, from 0.3 to 1.2 quercetin equivalents, which the authors attribute to differences in total polyphenols, ranging from 502 to 767 mg/kg across samples. On two routine authenticity checks, diastase activity averaged 22 shade units against a required minimum of 8, and sucrose was at trace levels.

Paired with Bupleurum spinosum pollen, methyl syringate could serve as a chemical marker for separating genuine Zantaz honey from other local or commercial honeys. Concentrations this high had previously been reported only in Manuka, Kanuka and Asphodel honeys, which come from plants in three different botanical orders. The authors also argue that recognising these activities could raise the commercial value of Zantaz honey for the poor rural communities in Morocco where it is made.

Six samples tested in cell cultures, at honey concentrations of 20 mg/mL or more, cannot show what Zantaz honey does in the human body, and the link to methyl syringate is a statistical correlation, not proof of cause. The authors add that nectar from the plant itself still needs analysing before methyl syringate can be tied directly to Bupleurum spinosum.