The word “nightshade” is often used in herbal medicines to refer a poisonous species of plant, but a highly regarded medicinal plant, belonging to the plant family Solanaceae. This plant is often called ‘deadly nightshade’ because of its toxic properties. Common name of this medicinal plant is ‘belladonna.’ Nightshade family is mainly known for its toxic and poisonous member plants and many of them are medicinal plants. However, the nightshade family i.e. Solanaceae family includes some of the most popular and economically important vegetable plants such as potatoes, tomatoes, tomatillos, brinjals or eggplants, chile peppers, bell peppers and jalapeno peppers also. These vegetables are very popular among consumers and are used by the whole world on daily basis. These vegetables are often referred as ‘nightshade vegetables’ or ‘Solanaceous vegetables.’ In other words, ‘Nightshade Vegetables’ are a group of vegetables belonging to the plant family Solanaceae.

Now let us have a look at the ‘Family-Wise’ classification of popular vegetables below for the better understanding of different types of vegetables:

  • Family: Aizoaceae -New Zealand Spinach (Tetragonia expansa)
  • Family: Chenopodiaceae -Beets (Beta vulgaris); Swisschard (Beta vulgaris var. cicla); Spinach (Spinacia oleracea)
  • Family: Compositae -Chicory (Cichorium intybus); Endive (Cichorium endivia); Lettuce (Lactuca sativa); Globe Artichoke (Cynara scolymus)
  • Family: Convolvulaceae -Sweet Potato (Ipomoea batatas)
  • Family: Cruciferae -Kale (Brassica oleracea var.acephala); Brussels sprouts (Brassica oleracea var.gemmifera); Cabbage (Brassica oleracea var.capitata); Cauliflower (Brassica oleracea var.botrytis); Broccoli (Brassica oleracea var.italica); Kohlrabi or Knolkhol (Brassica caulorapa); Rutabaga (Brassica napus var.napobrassica); Turnip (Brassica campestris var. rapa); Mustard (Brassica juncea); Chinese cabbage (Brassica chinensis and Brassica pekinensis); Radish (Raphanus sativus)
  • Family: Cucurbitaceae -Cucumber (Cucumis sativus); Bittergourd (Momordica charantia); Pumpkin (Cucurbita moschata); Sponge gourd or Towel gourd (Luffa cylindrica); Bottle gourd or Calabash gourd (Lagenaria siceraria)
  • Family: Euphorbiaceae -Tapioca or Cassava (Manihot esculenta)
  • Family: Leguminosae -Green Peas (Pisum sativum); Winged bean(Psophocarpus tetragonolobus); Cowpea (Vigna sinensis); Broad beans or Fava beans (Vicia faba)
  • Family: Malvaceae -Okra or Lady’s finger (Abelmoschus esculentus)
  • Family: Polygonaceae -Rhubarb (Rheum rhaponticum); Sorrels and Docks (Rumex vesicarius)
  • Family: Solanaceae -Potato (Solanum tuberosum); Brinjal or Eggplant (Solanum melongena); Tomato (Lycopersicon esculentum); Tomatillo, Chilli Peppers or Chile Peppers (Capsicum spp.)
  • Family: Umbelliferae -Carrot (Daucus carota); Parsley (Petroselinum crispum); Celery (Apium graveolens); Parsnip (Pastinaca sativa)
  • Family: Amaryllidaceae -Onion (Allium cepa); Leek (Allium porrum); Garlic (Allium sativum); Shallots (Allium ascalonicum); Chives (Allium schoenoprasum)
  • Family: Liliaceae -Asparagus (Asparagus officinalis)
  • Family: Araceae -Taro or Colocasia (Colocasia esculentum)
  • Family: Dioscoreaceae -Yam (Dioscorea alata)

Edible Parts of Solanaceous Vegetables: Based on the edible parts of the vegetables, they may be classified as fruit vegetables, leafy vegetables, root vegetables, and flower vegetables. In potatoes, stem tubers or modified underground storage stems are used as vegetables. In brinjals or eggplants, tomatoes, tomatillos, and chile peppers, the edible parts are fruits and seeds.

Nightshade Vegetables and Toxicity: Even though nightshade family contains some toxic plants such as belladonna, the food crops under this family are comparatively safe to eat. Tomatoes, eggplants, brinjals and chili peppers are not only safe foods but highly nutritious also. In fact, tomatoes and chili peppers such as bell peppers and jalapenos are considered as ‘vegetable superfoods’ due to the high nutrient-density of these foods.

There is a misconception about the toxicity of Solanaceous vegetables. Solanaceous vegetables may naturally contain negligible amounts of solanine which are not considered as toxic in minute quantities. However, in high amounts, solanine may be toxic, which is very unlikely to occur. No one eats high amounts of vegetables as staple foods.

What is Solanine? Solanine is a toxic glycoalkaloid compound found in the leaves, fruits and stems of all Solanaceous plants. In vegetable plants such as tomatoes, potatoes, eggplants, and chile peppers, the edible parts of the plants have negligible amounts of solanine which do not cause any health risks. However, do not eat leaves of Solanaceous plants as leaves may contain higher concentrations of solanine which may be toxic to health.

Food Poisoning of Green Potatoes: In one gram of edible potatoes, approx. 0.2g of solanine is present which is not toxic. Potato flesh contains very less solanine but potato peels contain more solanine content. When potatoes are exposed to light, they turn green due to the accelerated production of solanine. Such potatoes are not edible. Eating such potatoes may cause food poisoning.

Solanine Toxicity: If solanine is ingested in high amounts (200–400 mg), toxicity symptoms appear. Symptoms of solanine poisoning includes neurological disorders such as hallucinations, paralysis, head ache, dizziness, and temporary memory loss as well as gastrointestinal disorders such as dryness of throat, nausea, stomach ache, diarrhoea and vomiting. In children, a moderate amount of solanine (20–40 mg) is sufficient to cause toxicity.

Some major alkaloids present in nightshade vegetables: Apart from solanine, other alkaloids are also present in Solanaceous vegetables. For example, in tomato, tomatine is present. In chile peppers, capsaicin is present. Most of these alkaloids are antioxidants and beneficial for our health.

Allergy to Solanaceous/Nightshade Vegetables: Some people are allergic to nightshade vegetables due to the presence of alkaloids in these vegetables. Such people should not consume these vegetables in its raw form. Only cooked vegetables should be consumed in such cases as cooking minimises the content of allergens present in the vegetables.

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