It has been suggested that some of the flavones are modified by an enzyme in the
honeybee. If so, it seems likely that any transformation must occur in the presence of
enzymes in the saliva of the bees during collection. The simple aromatic compounds
found in propolis, also occur commonly in plants, and their presence in propolis is not unexpected.

E. L. Ghisalberti (1979) Propolis: A Review, Bee World, 60:2, 59-84, DOI: 10.1080/0005772X.1979.11097738

§

Propolis is a natural resinous mixture that honeybees collect
from different plants sources, such as tree buds, sap
flows, exudates and mix with bees wax and salivary enzymes

Casalone, & al. (2020). Propolis hosts a diverse microbial community. World Journal of Microbiology and Biotechnology.  36:50

§

There is another important question connected to the origin of
propolis and it concerns the chemical contribution of the honeybees. Of
course, the wax in propolis is mainly, or almost entirely, beeswax
(Negri et al., 2000), although many plant resins/exudates contain wax
and the plant wax contribution should not be totally ignored.

But what else do bees add to propolis? As bees take the plant resin with their
mandibles, inevitably some salivary enzymes are mixed with it. Indeed,
a few publications report the presence of small amounts of enzymes in
bee glue: α-amylase, β-amylase, maltase, some esterases (Kaczmarek
and Dębowski, 1983; Kędzia, 2011). β-Glucosidase activity in propolis
was also reported however, the authors did not identify the source of
this enzyme and speculated that it might have also come from the plant
source, and not necessarily from the bees (Zhang et al., 2011a). Much
speculation can be found in the literature about the “partial digestion”
of plant material by bees' enzymes during the production of propolis.

However, there is no positive evidence of such chemical changes. On
the contrary, several experiments based on parallel analysis of plant
resin taken from the source plant, resin taken from bees' corbiculae
(collected resin) and propolis from the beehive (“processed” resin with
added wax) have demonstrated that their chemical profiles are identical
and no chemical changes can be detected in the specialized plant metabolites
of the resin (Teixeira et al., 2005; Tran et al., 2012). Bolstering
this argument is the fact that enzymes are unlikely to have any activity
in resins/exudates (and propolis) due to the low water content and very
high phenolic content.

Bankova, & al. (2018). The phytochemistry of the honeybee. Phytochemistry Volume 155

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html