β-Boswellic acid

The aromatic resins frankincense and myrrh figure prominently in the Christmas story. These highly sought-after natural products, however, were known in North Africa and the Middle East for three millennia before the Christian era.

Frankincense, also known as olibanum, is derived from several species of trees in the Boswellia genus, notably B. carterii and B. sacra. It is a complex, gummy substance whose major components (≈30%) are boswellic acids. Of these triterpene acids, the β-isomer is the most prominent.

In 1932, A. Winterstein and G. Stein isolated the α-, β-, and γ-isomers of boswellic acid from olibanum “tears”. Over the next 30 years, several authors established their structures.

When the resin is steam-distilled to recover the frankincense essential oil, the acids remain behind. Nevertheless, the boswellic acids play a significant role in frankincense chemistry.

What about myrrh? Frankincense’s companion resin is isolated from small trees of the genus Commiphora, which is also in the Burseraceae family. Myrrh contains three major components: gum resin (polysaccharides and proteins), alcohol-soluble resins, and volatile oils (steroids, sterols, and terpenes).