Allistatin
Allistatin is the collective name for two chemicals, allistatin I and allistatin II, which are found in garlic. It is a sulfur-free chemical and plays an active role within garlic. It is most likely a flavonoid. There is no experimental evidence of the structure of allistatin; some studies claim it is similar to cyanidin, while others found it shared similarities with garlicin (but not allicin). References

Garlic
Organosulfur compounds