Propolis recently been isolated from red propolis, and prenylated acids such as 4-hydroxy-3,5-diprenyl cinnamic acid have been documented. An analysis of propolis from Henan, China found sinapinic acid, isoferulic acid, caffeic acid, and chrysin, with the first three compounds demonstrating antibacterial properties. Also, Brazilian red propolis, largely derived from "Dalbergia ecastaphyllum" plant resin, has high relative percentages of the isoflavonoids 3-hydroxy-8,9-dimethoxypterocarpan and medicarpin. Other flavonoids commonly present include galangin and pinocembrin. Caffeic acid phenethyl ester (CAPE) is also a component of some varieties of propolis from New Zealand. Occasionally, worker bees will even gather various caulking compounds of human manufacture, when
Rabbit-skin glue Rabbit-skin glue Rabbit-skin glue is a sizing that also acts as an adhesive. It is essentially refined rabbit collagen, and was originally used as an ingredient in traditional gesso. In traditional oil painting as practiced by the Renaissance painter, skin glue was used to coat the canvas. This is necessary because the linseed oil that forms the base of most oil paint contains linolenic acid that will destroy the canvas fibers over time. Though this did help to seal the canvas, they still had to cover it with another layer of a substance similar to paint in order to protect