From previous research we found that mechanically stressed living oranges quickly release high levels of certain volatile compounds, at least 10 times more than stressed dead oranges. Many of these volatile compounds are known or suspected insect repellents and therefore are a defense mechanism for the orange. We proposed that since there was a defense mechanism in the orange, that there should also be a repair mechanism likely using non-volatile substances. Our research showed up to 30% higher levels in polymethoxylated flavones in mechanically stressed living oranges when compared to control. Anthocyanins have been shown to have several health benefits in humans including anticarcinogenic activity and reduction of cardiovascular disease. Our goal in this new research is to determine if living blackberries would produce higher levels of anthocyanins, potentially as a repair mechanism, when mechanically stressed. In particular, we wanted to look at unripe and partially ripe fruit that does not have fully developed seeds postulating that the fruit would repair itself in order to propagate the species. Unripe or partially ripe blackberries were mechanically stressed by poking a stick pin though the berry. They were left on the plant for as little as a day and as long as a week. Stressed and unstressed berries that were of similar size, shape, and initial ripeness as the stressed berries at the time of the stressing event were harvested. Anthocyanins were extracted from the berries with methanol after grinding the berries to a fine powder in liquid nitrogen. The samples were centrifuged and filtered. Anthocyanins were separated by HPLC and detected by visible spectroscopy at 520 nm. Initial results look very positive. Visible inspection of the stressed berries showed significant more black color around the stress site, indicative of anthocyanin production, than the unstressed berries. Initial results of the HPLC showed an average 16-fold increase in the primary blackberry anthocyanin, cyanidin-3-O-glucoside, in stressed fruit compared to their unstressed counterpart (n=12). In addition, a second anthocyanin appeared in 67% of the stressed berries, but none of the control berries had the second anthocyanin.

Effect of mechanical stress on anthocyanin levels in blackberries

253rd National Meeting (2017)

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