One of the sweetest substances in the world is steviol glycosides, particularly Reb D and Reb M, which are extracted from the stevia plant (Stevia rebaudiana). However, if we consider the sweetest substances in nature, there are several other compounds worth noting:

Here are some of the very sweet natural and synthetic substances:

Steviol Glycosides:

Stevia extract, containing steviol glycosides, is about 200 to 300 times sweeter than sucrose.

Monellin:

This is a protein extracted from the tropical African plant Thaumatococcus danielii, which is about 3,000 times sweeter than sucrose.

Talatin:

Another protein from Thaumatococcus danielii, which is approximately 2,000 to 3,000 times sweeter than sucrose.

Sorbitol:

Although not as sweet as the above substances, sorbitol is a common sweetener that is about half as sweet as sucrose.

Saccharin:

An artificial sweetener that is about 300 to 500 times sweeter than sucrose.

Aspartame:

Another artificial sweetener that is about 200 times sweeter than sucrose.

Neotame:

A derivative that is even sweeter than aspartame, being about 7,000 to 13,000 times sweeter than sucrose.

Cyclamate:

About 30 to 50 times sweeter than sucrose.

Acesulfame K (Ace-K):

About 200 times sweeter than sucrose.

Sucralose:

Also known as Splenda, it is about 600 times sweeter than sucrose.

Among these substances, monellin and talatin are considered some of the sweetest substances in nature, while neotame is one of the sweetest artificial sweeteners known.

Please note that although these substances are extremely sweet, their usage and safety are strictly regulated, as excessive consumption of certain sweeteners may have adverse effects on human health.