A healthy lifestyle is a strategy to reduce the incidence of chronic diseases. Among other things, comprises a diet rich in fruits and vegetables and low in refined sugars and saturated fats. The World Health Organization (WHO) has indicated that 85% of cardiovascular diseases and a 15% of some cancers cases are associated with a low fruit diet (Wang, Li, Wang, Qiu, Shen & Wang, 2015), which is consistent with the Food and Agriculture Organization (FAO) statistics.

The world production of vegetable and fruits had achieved 1740 million tons for 2013 (950 million tons for vegetables and 760 million tons for fruits) (FAO, 2013). Colombian fruit production rose from 3.1 million tons in 2010 to 3.8 tons in 2014, which represents an increasing in annual rate of 5.0% Likewise, fruit and vegetables production in Colombia reached 46.2% from total agricultural sector production in 2013 (Asohofrucol, 2014).

In this sense, is clear that fruit and vegetables subsector is strategic for Colombian development. This is an opportunity to generate knowledge addressed to enables producers to acquire new tools to face the market challenges. Conversely, is important to study harvest and post-harvest losses, which are the most important limitation in fruits and vegetables industrialization. In fruits case, losses are related to high water content, ethylene production, breathing processes and maturity effect among them (FAO, 2013).

Treatment with antioxidant substances had achieved a preservation technique to diminish the effects of senescence processes caused by oxidation and subsequently, to control fruit post-harvest losses. There are several synthetic antioxidants used in foods and drugs in the market, including butylhydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary butyl hydroquinone (TBHQ) and propyl gallate, respectively. However, BHA and BHT use is associated with toxic and carcinogenic effects. The new generations of antioxidants are focus on natural additives, as plant extracts (rich in vitamin C, tocopherols, carotenoids and flavonoids) useful to protect products against oxidation (Barbosa, Bilbao, Vilches, Angulo, Fité, Paseiro & Cruz, 2014; Martín & Soliva, 2010; Tuesta, Orbe, Merino, Rengifo & Cabanillas, 2014).

Natural antioxidants are a topic of much scientific research due to its chemical properties and its food interaction. For instance, they can help in food conservation while reducing the risk of some diseases (cancer, heart problems and neurological disorders). In other words, they have a protective effect on health (Cerón, Higuita & Cardona, 2010; Freid, 2012). This protective effect is attributed to various metabolites including the group of polyphenols (flavonoids, anthocyanins, lignans, among others) (Muñoz, Ramos, Alvarado & Castañeda, 2007).

Colombian native fruits are a source of bioactive compounds with antioxidant activity, which can be used as natural additives (Zapata, Piedrahita & Rojano, 2014). An example of them, is the champa (Campomanesia lineatifolia Ruiz & Pav.), a fruit tree of the Myrtaceae family native from the Amazon. In Colombia, grows in Choco, Amazonas, Caquetá, Casanare, Cundinamarca and Boyacá departments. This fruit has a high concentration of acids (citric acid predominating) and sugars (mostly sucrose). Therefore, its total titratable acidity is close to 3% and total soluble solids (TSS) are between 11.2 and 13.4% (Álvarez, Galvis & Balaguera, 2009; Balaguera, Álvarez & Bonilla, 2009).

Even though there are a small number of studies related to champa phytochemicals, the presence of three triketones in seeds and nine volatile compounds isolated from pulp, peel, leaves and seeds is demonstrated. In fact, these compounds show antimicrobial activity and potential use as colorants or additives in food matrices (to improve functional characteristics or shelf life extension) (Bonilla, Duque, Garzón, Takaishi, Yamaguchi, Hara & Fujimoto, 2005).

In fact, in a previous work carried out by Balaguera, Álvarez & Bonilla (2009), harvest and post-harvest losses of champa had achieved 97% in the Lengupá Province of Boyacá, Colombia. In this context, the development of new products obtained from champa is a strategy to improve the benefits to producers, despite having enriched phenolic extracts, which were obtained through solid liquid extraction process of champa (Muñoz, Chávez, Pabón, Rendón, Chaparro & Otálvaro, 2015). The results confirmed antioxidant activity and phenolic compounds presence on the extracts. To continue with this research, this work aimed to evaluate microwave extraction with different conditions as an alternative extraction method. In this research, different conditions of extraction time, microwave power and solvent looking for cheaper, easily, safe and environmental friendly extraction conditions to carry out this process, were considered. The results will contribute to the species knowledge and as source of phenolic compounds useful for food industries.

The fruits of C. lineatifolia came from the municipality of Miraflores (Boyacá, Colombia 5°11״47׳N 73°08״40׳O). The mean fruit weight ranged from 25-30 g and their ripening degree ranged from 3 to 6, equivalent conditions to green, ripe and overripe, respectively. Champa fruits were selected by their physics attributes (without wounds, fermentation, fungal or insect damage). After selection, fruits were scalded to inactivate enzymes prior to pulp production (Muñoz et al., 2015). Pulp was obtained and subsequently, was dehydrated into a freeze-dryer (FreeZone Plus 12 Liter, Labconco (r)) until 6% of moisture (experimental conditions: 24 h, 0.12 mBar and -89 °C). Dehydrated pulp was stored at -20°C in airtight containers protected from light until microwave extractions.

Microwave extraction yields have had achieved a similar behavior of the results obtained in solid-liquid extractions of champa fruits, where aqueous extracts present the highest yields (reaching efficiencies from above 45%) (Muñoz et al., 2015). Although, statistically significant differences were observed in the extraction yields respect to power and extraction time (95% confidence interval) for all evaluated variables (solvent, time and power). The highest yield extraction was 67.68 ± 18.20%, which was higher than the results obtained with solid-liquid extraction. The extraction conditions from which this yield had achieved were 100W, 2min and water as solvent. These results are comparable in variability to the report by Martínez, Contreras & Belares (2010); Muñoz et al. (2015); Alonso, Aguilar, Vernon, Jiménez, Cruz & Román (2017), where the application of ultrasonic or microwave extraction have allowed an increasing in the rate of mass transfer and thus the extraction yield of antioxidant compounds from plant material.

The phenolic compounds extraction are thought was independent of power and time and only the solvent, presented a statistically significant effect (confidence interval 95%) at the evaluated conditions. In this sense, at higher solvent polarity an increasing in the extraction feasibility of phenolic compounds was observed (Martínez, Contreras & Belares, 2010; Alonso et al., 2017). On the other hand, the solubility in water and alcohol of phenolic compounds is higher for diphenols and polyphenols such as flavonoids, suggesting their presence in the studied matrix (Cerón, Higuita & Cardona, 2010).

The phenolic compounds concentration obtained from champa fruits was lower than the value established for Guabiroba Brazilian (C. adamantium) (7240 - 21190 μg of gallic acid.g¹ of dry sample). However, was comparable to other fruits and tubers, for example, carambola (Averrhoa carambola L.) (13.10 μg of gallic acid.g^-1 of dry sample) and sapodilla (Manilkara zapota L. P. Royen), (1.421 μg of gallic acid.g^-1 of dry sample) (Rodríguez, López & García, 2010).

Bearing this in mind, the present work is intended to present phenolic compounds extracted by solid-liquid extraction from champa fruits, it was observed that using this technique after 4 h of extraction with a mixture of ethanol-water (70:30) as solvent at 70°C, the amount of those compounds was 5272.51 ± 424.89 μg of gallic acid.g^-1 of dry pulp. In this sense, the results obtained by microwave extraction were lower than solid extraction results (Muñoz et al., 2015). It was also noted in Table 2, in most treatments FRAP values were approximately twice as those obtained through DPPH. Nevertheless, is possible that some antioxidant compounds, such as carotenoids and some sugars can interfere in the measurement of DPPH methodology (Pérez, Lugo, Gutiérrez & Del-Toro, 2013).

It was observed that antioxidant activity measured through DPPH method was affected by time, solvent and power (P<0.05) while by FRAP method was only affected by solvent and power (P<0.05). In both cases, this parameter had achieved an increasing effect with time and power used in extraction process.

When the results were compared against the antioxidant activity obtained by solid-liquid extraction using water as solvent at 50°C (6.31±0.61 and 7.90±1.05 mg of Trolox.g^-1 of dry pulp for DPPH and FRAP methods, respectively), is clear that microwave extraction have allowed to achieve better results (Muñoz et al., 2015).

On the other hand, in both extractions, fruit extracts with higher phenolic content had the higher antioxidant activity. It shows that biological activity is attributed exclusively to the phenolic compounds. Although in previous studies have determined a direct relationship between the phenolic compounds concentration in different fruit extracts and their antioxidant activity, is possible that in extractions with solvents such as water, these compounds had formed macromolecules and then, extracts, which had a lower antioxidant activity than it was expected.

When comparing the results of antioxidant activity obtained in this study with previous reports, we found that for different species, including carambola, the antioxidant activity was 8.00 mM TEAC.g^-1 from wet pulp, which is very close to the maximum obtained for champa (C. lineatifolia) fruit. However, fruits such as yacon (Smallanthus sonchifolius (Poepp.) H.Rob.), noni (Morinda citrifolia L.), cherry (Prunus avium (L.) L.), banana (Musa acuminata Colla.), passionfruit (Passiflora edulis Sims.) and camu-camu (Myrciaria dubia (Kunth) McVaugh.), had achieved higher activities 22.20 mM TEAC. g¹ of pulp (Morillas & Delgado, 2012).

Considering results related to antioxidant activity, this paper has shown that the extracts obtained had potential in agroindustrial processes. Conversely,in meat products, they can be used to control lipid oxidation. Alternatively, in baking, they can increase the functional properties as well as to enrich products with antioxidants. In dairy industry, are used to increase the concentration of biologically active compounds in these products and finally, in fruits and vegetables industry, they can help to control the oxidation and can be used to extend the shelf life of products. In addition, natural antioxidants are also employed as raw materials for the pharmaceutical and cosmetic industries due to its antioxidant activity, moisturizing and emollient activity (Rodríguez,López & García, 2010).

This study evaluated the effects of fruit the extracts obtained by microwave extraction, which have demonstrated that had potential in agroindustrial processes due to their antioxidant activity. Given these concerns, the fruit extracts offers a new way to take advantage of this native amazon fruit as a source of extracts, which can be used as functional additives in other food matrices, adding value to this species.

The best results for extraction had achieved using water as solvent; this provides more accurate and reliable estimates of an advantage for food industry because water is a green and nontoxic solvent. On the other hand, short times involved in microwave phenolic compounds extraction compare with other extraction methods; helps ameliorate process cost in the industrialization of this process.