Antioxidant and antimicrobial properties of ethanolic extracts of guarana, boldo, rosemary and cinnamon

Abstract

In this investigation, the ethanolic extracts of two less known plants, little reported in the literature (guarana and boldo leaves) were studied in comparison with the ethanolic extracts of two well studied plants (cinnamon and rosemary), regarding their colour, GC-MS profile, phenolic content and their antioxidant and antimicrobial properties. The rosemary (59.20 ± 0.28) and guarana (56.63 ± 0.54) extracts showed the highest values for luminosity (L*) and the UV-Vis absorption increased when L* decreased. GC-MS identified a limited number of compounds in the cinnamon and guarana extracts. The cinnamon extract showed the highest value for the total phenolic content (172 mg GA/g extract) as compared to the other extracts. The highest antioxidant capacity was observed for the boldo leaves extract in the TEAC (6.66 ± 0.17 mM) assay and for the rosemary extract in the DPPH (0.80 ± 0.14 mg/L) test. In addition, all the extracts showed antimicrobial activity against the S. aureus strain, indicating that all the extracts studied could be used by food industries to develop new active food packaging materials.Keywords: Herbs; Seeds; Phenols; Volatile compounds; S. aureus; E. coli. ResumoNesta investigação, foram estudados dois extratos etanólicos de plantas pouco conhecidas na literatura (guaraná e boldo-do-chile), em comparação com os extratos etanólicos de duas plantas bastante estudadas (canela e alecrim), quanto aos parâmetros de cor, perfil GC-MS, teor fenólico e propriedades antioxidantes e antimicrobianas. Os extratos de alecrim (59,20 ± 0,28) e guaraná (56,63 ± 0,54) mostraram os maiores valores de luminosidade (L*). A absorção de radiação ultravioleta visível (UV-Vis) aumentou de intensidade quando o valor L* diminuiu. Na análise do perfil GC-MS, identificou-se um número limitado de compostos nos extratos de canela e guaraná. O extrato de canela apresentou o maior conteúdo de compostos fenólicos totais (172 mg GA/g extrato), em comparação com outros extratos. A maior capacidade antioxidante foi observada para o extrato de boldo-do-chile, no ensaio TEAC (6,66 ± 0,17 mM), e para o extrato de alecrim, no teste de DPPH (0,80 ± 0,14 mg/L). Adicionalmente, todos os extratos mostraram atividade antimicrobiana contra a cepa S. aureus, indicando que todos os extratos estudados podem ser utilizados pelas indústrias de alimentos para desenvolver novos materiais ativos de embalagem de alimentos. Palavras

Gelatin‐chitosan edible film activated with Boldo extract for improving microbiological and antioxidant stability of sliced Prato cheese

“…Moreover, Bonilla & Sobral () developed and characterised active films based on gelatin:chitosan blends, incorporating Boldo extract, at 1%. The first study confirmed six main compounds (1,8‐cineol, ρ‐cymene, phytol, eicosanoic acid, cis,cis,cis‐7,10,13‐hexadeca trienal and α‐irone) and the good antioxidant and antimicrobial activity of Boldo extract (Bonilla & Sobral, ). The second study reported that films based on blended biopolymers (GEL50:CH50), with Boldo extract at 1%, showed good physical properties (more resistant and extensible films, with reduced water vapour permeability and considerable protection against UV light), as well as a potential antioxidant and antimicrobial activity Bonilla & Sobral ().…”

“…To our knowledge, research on the application of active films to inhibit the undesirable growth of microorganisms and fat oxidation, in sliced Prato cheese during storage, is limited. In this sense, Bonilla & Sobral () previously reported the identification of components (using GC‐MS profile), the antioxidant activity (using three different assays) and antimicrobial activity (against Escherichia coli and Staphylococcus aureus ) of Boldo extract, among others. Moreover, Bonilla & Sobral () developed and characterised active films based on gelatin:chitosan blends, incorporating Boldo extract, at 1%.…”

Active edible coatings with Boldo extract added and their application on nut products: reducing the oxidative rancidity rate

“…2). According to Bonilla et al (2012), films made from proteins and carbohydrates are excellent barriers to oxygen, because of their tightly packed, ordered hydrogen-bonded network structure. Thus, oxidation could be effectively reduced by selecting films and coatings of limited oxygen permeability.…”

“…However, their high content of unsaturated fatty acids makes them susceptible to oxidative rancidity if stored sub-optimally or for too long, especially when shelled (Shahidi & John, 2013). The oxidation process leads to quality deterioration of the nuts (rancid odours and flavours, a decrease in nutritional quality and the formation of potentially toxic compounds) (Atar es & Chiralt, 2016), being the most common indicators of lipid rancidity, the peroxide value (PV) and hexanal levels (Bonilla et al, 2012).…”

“…In earlier investigations, the authors studied the antioxidant and antimicrobial properties of four different ethanolic extracts (Bonilla & Sobral, 2017b), as well as developed active films based on gelatin-chitosan blends (Bonilla & Sobral, 2016) and gelatinsodium caseinate blends (Bonilla & Sobral, 2017a), both using Boldo-of-Chile extract. Based on some previous results, the pure and blended edible coatings that presented the best antioxidant activity were chosen to be applied on Brazil and Cashew nuts, with the main objective of study the application effect against lipid oxidation during storage.…”