I first heard this term used around 1981-2ish, and I never found out what this means. Back then, it was predicted that left-handed sugar would be a calorie-free sugar soon to replace Sweet 'n Low. This was especially important when they thought saccharine caused cancer (but I hear the school of thought has changed in recent years). This was all prior to the creation of Nutrasweet. There was no Equal or Sugar Twin yet.
The collective educated WAG is that it must be an isomer of a sugar molecule where (typically) everything is the mirror image. However, this term was specifically referring to sucrose. As I recall, sucrose is a symmterical, hexagonal shape. So, this doesn’t seem to make sense. Although, I WAG it still could be some isomer of sucrose with a carbon chain down the “centerline” of the molecule and the OH groups all attached to the left side of the carbon chain? But, I’m no chemist…
It seems left-handed sugar has now been approved in the US as a sugar substitute. It is being marketed under the tradename “Splenda”. I have found some hot cocoa using it, but nothing else yet…other than “Splenda” itself sold in a bright, yellow box.
Any organic chemists or bio-chemists out there who can explain and/or correct my post? - Jinx
P.S. I always joked a left-handed sucrose molecule would be ambi-dextrose!
The sugar concerned is most likely glucose. From Webster’s: “a sugar C6H12O6 known in dextrorotatary, levorotatory, and racemic forms”. The dextrorotatory form of glucose is known as dextrose, so your ambi-dextrose pun was actually quite close to the mark. It is, as you opined, an isomeric form of the sugar. The dextrorotatory form is digested and absorbed, the levorotatory form is passed on through.
Left handed sugars are, as you noted, mirror images of regular sugars. As a result, I believe that our enzymes are unable to affect them the way they do with regular sugars. One thing I’ve always wondered is if LH sugars would foul up your insulin levels, Splenda apparently does not.
Sorta. It’s based on a hexagon of carbon, but each carbon has an -OH and an -H group coming off it. It’s the relative orientation of these groups that makes it asymmetrical.
“Left handed” Sucrose would be a mirror image of the entire molecule. You would have to look at the structure to see that they are non-superimposable images. It would be quite difficult to make in large quantities of it since none of it’s components would exist in nature. Our enzymes might not digest it, but our taste buds might not taste it since it might not fit into the receptors properly. I am not a biochemist though so I do not know.
Sucrose is actually a disaccharide. It’s made by attaching a glucose molecule to a fructose molecule. Its shape is not symmetrical. It looks sort of like two of those hexagonal shapes that everyone remembers. The sugar monomers that make up sucrose are themselves not symmetrical. Thus there are two forms of glucose,
and two forms of fructose. (Sorry, can’t draw sucrose with the code command)
If you connect up a glucose and a fructose to make sucrose you’ll find that there are 4 possible forms; glucose made from the 2 D sugars, the 2 L sugars, or from the 2 DL combinations. All will have different properties. Only the sugar made entirely of D sugars will be used by the body. Bacteria may digest some of the other forms. Feeding odd sugars to your intestinal bacteria might have unpleasant consequences, which could explain why none of these miracle sweeteners have been marketed.
Going off-topic a bit - this bit of scientific knowledge played a key role in Dorothy L. Sayers’ The Documents in the Case, although in that case it was (naturally enough) concerned with isomers of a mushroom poison.
