Potatoes: Food or Poisons?

Potatoes are the fourth most widely grown crop in the world. However, they’re also a part of the infamous nightshade family: Solanaceae. Related to the deadly nightshade: Atropa Belladonna [1], potatoes carry the same toxins that Atropa Belladonna is equipped with. Potatoes are comprised of many compounds with biological activity including: glycoalkaloids (the primary toxin), protease inhibitors, lectins, and phenolic compounds.[2]  This article aims to briefly discuss the toxins that potatoes can carry and address the fact that chemical poisons are easily accessible in day-to-day life.

nightshade
Figure 1: An Atropa Belladonna berry: Accidental ingestion of berries are treated with emetics, medications to induce vomiting

Potatoes are indigenous to the Andes mountain between Chile and Peru. Genetic mapping has linked them back to Solanum Tuberosum, the original ancestral potato. [3] The most well-characterized toxins in potatoes are the glycoalkaloids: solanine and chaconine. The formation of these compounds in potatoes is driven primarily by light induced stress. To put it in english, potatoes exposed to sunlight have a high likelihood of being eaten by an animal. As a response to sunlight and the fear of being a possible meal, potatoes turn green due to an increase in chlorophyll and also release foul-tasting toxins: the glycoalkaloids. This gives green potatoes their characteristic bitter taste, and is identical to the compounds produced by Atropa Belladonna.

Applicable to your daily lives, avoid green photosynthesizing potatoes. Chaconine is highly localized to the sprouts of the potato so cut them off before eating them. Moreover, cooking is ineffective at significantly reducing chaconine levels where boiling reduced chaconine and solanine levels by 3.5% and 1.2% respectively. [4] However, virtually all glycoalkaloids was removed from the potato via peeling the skin ~3-4mm from the surface. Thus, peeling potatoes may be effective in prevention of glycoalkaloid poisoning.

screen-shot-2016-11-12-at-1-01-23-pm
Figure 2: Solanine, the primary glycoalkaloid found in potatoes. Can cause vomiting, diarrhea, and abdominal pain in high concentrations [5]
Solanidine metabolism levels were measured in three humans, given radioactive labeled solanidine. 90% of solanidine disappeared from the blood within 20 minutes. However, the rate of excretion in the urine was low ~1-2% which led researchers to believe sequestration of solanidine had occurred. The site of sequestration on mobile carriers turned out to be red blood cells and Claringbold, 1982 suggested that the solanidine could be released in times of stress, like pregnancy. Solanidine was also suggested to possibly be retained on sterol groups, determined by radioimmunoassay. [6] This relatively long serum half-life in the blood is quite intriguing, because a different paper cited the other alkaloids to break down more quickly via some biotic hydrolysis step. [7]

This article went briefly into the presence of a toxin in potatoes and a few characterizations of the toxin and metabolism in the body. In my next article, we’ll be looking at something very different, an optical system: Fresnel lens and applications to real life. I’ve chosen the subject because I just finished a microscopy class here on campus, and think it would be a good way to dedicate a kind of memoir to the class and old school/ new school optics.

Your Friend,

Joseph

2 Replies to “Potatoes: Food or Poisons?”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s