Page 5 - Science Focus (Issue 017)

saccharin [6, 7], and these conditions do not apply to
humans at all [8]. WARNING: NEVER TRY THIS IN
You may be wondering how can a molecule like YOUR SCHOOL LAB!
saccharin, that is not sugar, tastes sweet? This is actually
a result of its specific molecular shape, allowing it to Although it may seem tempting to touch and taste the
trigger sweet taste receptors on the tongue through chemicals and biological samples in your school lab,
a lock-and-key mechanism. These receptors transmit and you might make great discoveries…most chemicals
electrical impulses to the brain, creating the perception are not safe to consume or handle. It is always a good
of sweetness. The structural requirement for molecules practice to wear gloves in the laboratory and to wash
that act as “keys” to the sweet taste receptor “lock” is your hands thoroughly afterwards. Most importantly,
described as a “triangle of sweetness” [9]: it needs to NEVER taste or consume any laboratory chemicals!
contain two sites for forming hydrogen bonds with the
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receptor — one with an O–H or N–H group and one with
an O or N atom — and a third site of a water-repelling
group (e.g. hydrocarbon), forming a triangular geometry such as aspartame “Equal ” and
TM
within specific dimensions (Figure 1(a)). This configuration sucralose (Splenda ). More recently,
TM
is demonstrated in saccharin (Figure 1(b): an N–H group, sugar alcohols (e.g. erythritol and
one of the oxygen atoms on sulfur and the hydrophobic xylitol) and plant extracts (e.g. Stevia
benzene ring) [10], allowing it to bind perfectly into the and Monk Fruit) are trending as
sweet taste receptor’s cavity. This same phenomenon “healthier” natural sugar substitutes.
also occurs for other sweet-tasting substances, such as Consumers today should be
glucose, sucrose or aspartame. content that such a wide range of
However, evidence suggests that saccharin also sweetening options are available
activates other taste receptors on the tongue, including in the market, offering them the
the T2R bitter taste receptor and the vanilloid receptor sweetness of sugar without the
1 (TRPV1). These may explain the bitter and metallic risks of weight gain or developing
aftertaste of saccharin, respectively [11]. diabetes!

This first commercialized artificial sweetener,
saccharin “Sweet’N Low TM ”, had inspired the
development of similar products with improved tastes,

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