Give me a resin

What is it?

Is there a more evocative Christmas smell than the fragrance of a fresh pine tree? Mulled wine with cinnamon spices or a roasting turkey are close contenders for the prize, but for literary purposes let’s opt for the heady scent of a Christmas Fir. That rich winter wonderland terpentine-like citrus aroma is the product of several molecules (read more here, the most significant of which is pinene.

Pinene is a terpene found in the resin of pine trees, and as well as generating the distinctive coniferous scent, it is also a potent inhibitor of the human Cytochrome P450 2B enzyme. CYP450 proteins are a superfamily of enzymes essential for hormone, cholesterol and vitamin D synthesis and metabolism. They also assist in the clearance of toxins from the body via the liver. So, if you ever you needed a “resin” not to eat your Christmas tree…

What does it look like?


Researchers determined the crystal structure of (+)–α-pinene bound to CYP450 2B6 to better understand how this pine tree molecule can bind, inhibit, and alter the enzyme1. This is important to learn about how the enzymes generally interact with a diverse range of substrates.

(+)-α-pinene binds tightly at the CYP450 2B6 active site. The CYP450 2B6 active site is remarkably flexible and moves and shifts to mould around the pinene molecule as it binds.

Where did the structure come from?

This structure is of human CYP450 2B6 and is PDB ID 4I91.


  1. Wilderman et al., Journal of the American Chemical Society 2013: 135: (10433-10440)

Pinene – It’s beginning to smell a lot like Christmas!

What does it look like?

Pinene crystallises in an Orthorhombic P212121 space group. Graphics created using CrystalExplorer

Pinene crystallises in an Orthorhombic P212121 space group. Graphics created using CrystalExplorer

What is it?

pinnie_2As I write this post, sitting in a very wintery northern hemisphere, the nights are drawing in and the temperature is dropping to the low single figures (being the UK, it is also raining, but we’ll try to forget that bit). However, being a native to these shores, there’s nothing quite like it to make you feel like Christmas is getting close.

A decorated Christmas tree, with its twinkling lights and colourful decorations, is probably one of the most iconic Christmas images. Although it may be unwise to start a debate about the merits of natural vs. artificial, it is hard to deny that a fresh tree definitely wins in the scent department.

That smell comes from Pinene. Pinene is a naturally occurring hydrocarbon, part of the terpene family, and is most commonly found in tree resin – the thick, sticky liquid secreted by conifers when they’ve been cut or wounded. Pinene is predominantly used by these trees to seal and protect wounds, and to act as a repellent to harmful insects. Pinene is also found in many essential oils (such as ironwort or sage), used as flavour additives in food, perfumery and in medicines and alternative medicines. It is also the main component of turpentine paint thinner, and can be used as a feedstock for jet fuel!

Where did it come from?

This structure was determined and published by Andrew Bond and John Davies of the University of Cambridge in 2001 (A. D. Bond, J. E. Davies, Acta Crys., 2001, E57, o1039). Graphics were produced using CrystalExplorer. Further facts were also found on