Difference Between Flavonoids and Isoflavonoids

The key difference between flavonoids and isoflavonoids is that flavonoids have the 2-phenylchromen-4-one backbone in their chemical structure, while isoflavonoids have the 3-phenylchromen-4-one backbone in their chemical structure.

Flavonoids represent one of the largest and most studied polyphenolic secondary metabolites found in plants. They have two main groups based on chemical structure: flavonoids (bio flavonoids) that have 2-phenylchromans structure and isoflavonoids that have 3-phenylchromans structure. Flavanones, flavones, flavonols, flavan-3-ols, and anthocyanidins are several flavonoids, while isoflavones, isoflavans, and pterocarpans are several isoflavonoids. Both groups have very important benefits such as high antioxidant power, longevity, and weight management.

1. Overview and Key Difference
2. What are Flavonoids
3. What are Isoflavonoids
4. Similarities Between Flavonoids and Isoflavonoids
5. Side by Side Comparison – Flavonoids vs Isoflavonoids in Tabular Form
6. Summary

What are Flavonoids?

Flavonoids or bioflavonoids are a group of flavonoids that have the 2-phenylchromen-4-one backbone in their chemical structure. This group includes flavanones, flavones, flavonols, flavan-3-ols, and anthocyanidins. It comprises a diverse class of polyphenolic compounds with antioxidant power. They are commonly found in leaves, bark, roots, flowers, and seeds of plants. Several members of this group have received broad attention from the public due to their benefits in the field of human nutrition. For example, proanthocyanidins in grape seeds, flavanones (hesperidin) in citrus, flavonols (quercetin) in onions and other vegetables, catechins in green tea, and anthocyanosides in bilberry.

Difference Between Flavonoids and Isoflavonoids

Figure 01: Flavonoids

Flavones are one of the important members of flavonoids. Flavones are widely distributed in leaves, flowers and fruits. The major sources of flavones are celery, parsley, red peppers, chamomile, mint and ginkgo biloba. Flavonols are flavonoids with ketonic group. Flavonols are mainly present in a variety of fruits and vegetables. The most studied flavonols are kaempferol, quercetin, myricetin and fisetin. Flavanones are generally present in all citrus fruits such as oranges, lemons, and grapes. The most studied flavanones are hesperetin, naringenin and eriodictyol. Moreover, flavan-3-ols catechin is abundantly found in bananas, apples, blueberries, green tea, peaches, and pears. Anthocyanins are also a member of this group; they are pigments responsible for colours in plants, flowers and fruits. The most widely studied anthocyanins are cyanidin, delphinidin, malvidin, pelargonidin, and peonidin.

What are Isoflavonoids?

Isoflavonoids are a group of flavonoids that have the 3-phenylchromen-4-one backbone in their chemical structure. Isoflavonoids such as isoflavones have no hydroxyl group substitution at position 2. Isoflavonoids are a class of biologically active phenolic compounds. As their biological effect is via the estrogen receptor, sometimes they are referred to as “phytoestrogens”. Though the medical and scientific community are skeptical about their use, they have been widely used in many dietary supplements. Some isoflavonoids were identified as toxins, such as biliatresone. Biliatresonemay causes biliary atresia when infants are exposed to the plant product. The isoflavonoids group is broadly classified into subgroups including isoflavones, isoflavonones, isoflavans, pterocarpans, and rotenoids.

Key Difference - Flavonoids vs Isoflavonoids

Figure 02: Isoflavonoids

Isoflavonoids are derived from the flavonoid biosynthesis pathway via liquiritigenin or naringenin. The most widely studied isoflavonoids are genistein, daidzein, and homoisoflavonoids.

What are the Similarities Between Flavonoids and Isoflavonoids?

Flavonoids and isoflavonoids are polyphenolic secondary metabolites.
Both are derived from plants.
They have antioxidant properties.
Both are phytonutrients (plant chemicals).

What is the Difference Between Flavonoids and Isoflavonoids?

Flavonoids have the 2-phenylchromen-4-one backbone in their chemical structure. In contrast, isoflavonoids have the 3-phenylchromen-4-one backbonein their chemical structure. So, this is the key difference between flavonoids and isoflavonoids. Furthermore, flavonoids have less antioxidant activity compared to isoflavonoids.

The below infographic lists the differences between flavonoids and isoflavonoids in tabular form.

Summary – Flavonoids vs Isoflavonoids

Flavonoids are a class of polyphenolic secondary metabolites found in plants. They are derived through flavonoid biosynthesis pathway. They have the general structure of a 15-carbon skeleton. This structure consists of two phenyl rings and a heterocyclic ring. Based on chemical structure, they are two types: flavonoids and isoflavonoids. Flavonoids have the 2-phenylchromen-4-one backbone in their chemical structure. In contrast, isoflavonoids have the 3-phenylchromen-4-one backbonein their chemical structure. Thus, this is the key difference between flavonoids and isoflavonoids.

Reference:

1. Dixon, Richard A., and Giulio M. Pasinetti. “Flavonoids and Isoflavonoids: From Plant Biology to Agriculture and Neuroscience.” Plant Physiology, American Society of Plant Biologists, 1 Oct. 2010, Available here.
2. Panche, A N, et al. “Flavonoids: an Overview.” Journal of Nutritional Science, Cambridge University Press, 29 Dec. 2016, Available here.