Literature review: 'Phenolic compounds and antioxidant activities of edible flowers from Thailand'

This is the first literature review in a series exploring the personal and environmental benefits of flowers. This post will look at "Phenolic compounds and antioxidant activities of edible flowers from Thailand" from the Journal of Functional Foods.

Cassia siamea

Flowers as foods have traditionally been used in European, Asian, East Indian, Victorian English, Middle Eastern, and even early American cooking (89).

This article investigates the phenolic compounds, antioxidant properties and nutritional value of 12 edible flowers from northeastern Thailand "which have been long consumed as vegetable and used as ingredients in cooking" (88). The authors introduce the article by saying how high intakes of fruits and vegetables have been associated with a lower incidence of chronic diseases such as cardiovascular disease and cancer -- "health benefits attributed to the antioxidant capacity derived from the phenolic compounds present in edible plants" (88). 

"In Thailand, many flowers have been eaten since ancient times, and some have medicinal properties as well as nutritional value" (89). Here in the United States, we are surrounded by a culture of convenience where many foods are processed and filled with additives and artificial ingredients, centered around energy and calorie content versus nutrition density. It therefore seems worthwhile to observe other cultures that do incorporate edible flowers into meals and find out more about their nutritional value.

Tagetes erecta

Twelve fresh edible flowers were collected from the northeastern region of Thailand for experimentation. According to the article, "phenolic compounds are a large and diverse group of phytochemicals, which includes many different families of aromatic secondary metabolites in plants" (88). "Phenolic compounds have strong in vitro and in vivo antioxidant activities associated with their ability to scavenge free radicals, break radical chain reactions and chelate metals" (88). The authors used RP-HPLC analysis to identify the phenolic compounds of edible-flowers extracts (93).
 

The results: "the data of twelve edible flower samples in the present study indicate that edible flowers were a rich source of phytochemicals, with high levels of phenolic compounds and antioxidant  activities" (96). The study revealed that, of the twelve varieties, yellow flowers exhibiting higher flavonoid content were likely to have higher antioxidant potential than other colors. With these results, the authors hope readers will utilize edible flowers as sources of phytochemicals but with caution as toxicity of the plant extracts with high antioxidant activity should be tested to confirm their safety for use as food additives. 

Khee lek (Cassia siamea): highest value of total phenolic content

Daao rueang (Tagetes erecta): highest total flavonoid content

Puangchompoo (Antigonon leptopus) and Tagetes erecta: highest ferric reducing antioxidant power and value

I've included a snapshot of the table describing the tested edible flowers in detail, below:

Table 1 - The characteristics and biological activities literature of the selected edible flowers http://dx.doi.org/10.1016/j.jff.2011.03.002

Works Cited: Onanong Kaisoon, Sirithon Siriamornpun, Natthida Weerapreeyakul, Naret Meeso. “Phenolic compounds and antioxidant activities of edible flowers from Thailand.” Journal of Functional Foods, Volume 3, Issue 2, April 2011, Pages 88–99. <http://dx.doi.org/10.1016/j.jff.2011.03.002>