Does juice lose its nutritional content as it gets less fresh?

i have an industrial juicer at home and just juiced some carrots and kale. I have extra and was planning on leaving it in the fridge for tomorrow. Does it lose nutritional value as it gets older? I'm also curious about this same question for produce. I have noticed that when I picked greenbeans off the vine they were sweet and delicious. By the next day, they just tasted like normal greenbeans. Is there an oxidizing process by which they lose their sugars and/or nutrients?