For an herb so common and robust, Plectranthus amboinicus has been given a surprising number of international aliases: Mexican mint, Cuban oregano, Indian borage, and Spanish thyme, amongst others. Despite its global affiliations, the plant is native to Southern and Eastern Africa. The sheer variety of its names also belies its botanical ancestry- it belongs to the Lamiaceae family, which includes common herbs such as basil, mint, oregano, sage, rosemary, and thyme.
P. amboinicus, as we shall so refer, is characterized by large, thick, opposite, heart-shaped leaves, with a scalloped edge, tapering to a point. When healthy, its leaves are a beautiful jade green, and covered with short, soft fuzz. Its fleshy, cuboidal stems are similarly bedecked, and can grow to a height of almost a metre. The almost defining characteristic of the plant is its distinct smell, a pleasant oregano-like fragrance. This has in turn given rise to its rather poetic name in Mandarin: ‘dao shou xiang’, or ‘fragrant when touched’. It flowers in the summer, sending forth lovely pale purple or white blooms. However, it has not been observed to flower in hot tropical countries such as Singapore.
As a garden herb, P. amboinicus holds much appeal: it is easy to grow from stem cuttings, and surprisingly tolerant of the negligent or novice gardener, either too miserly with the watering can, or prone to an effusive showering of love- although, of course, moderation is nonetheless preferred. It seems almost to speak to its Human- too little sun, and the leaves turn a dark green; too much sun, and they curl and turn yellow.
Besides being used to flavour meat and poultry, P. amboinicus boasts an impressive list of ailments it is thought to be effective against. Anecdotal evidence exists of its ability to cure chronic coughs, either by chewing the leaves, pounding them with some water, or steeping them and drinking the tea. Rubbing the leaves and inhaling the vapour is thought to help clear blocked noses, much like menthol-based nasal decongestants. Leaf pulp applied to the skin is thought to soothe burns, sores, bites, and inflammatory skin conditions such as eczema. The same anti-inflammatory property seems to hold true even when the tea is consumed- it is thought to help treat bronchitis, asthma, malaria, helminths (worms) and diseases caused by viruses. In fact, scientists in Taiwan have investigated the efficacy of P. amboinicus in treating rheumatoid arthritis, and found that it was able to reduce the levels of proteins that mediate and indicate inflammation, known as pro-inflammatory cytokines, in rats. In addition, the herb has been used against pain, insomnia, and diarrhoea, to increase lactation in new mothers, and is also thought to have some hepatoprotective (liver protective) effect.
Some may scoff at the idea of herbal folklore, but its wide and continued use in India, Africa and Southeast Asia suggests that there may be truth to the claims. After all, many Western medicines we use today contain compounds first isolated from plants, including Vinblastine from the rosy periwinkle, which is used in the clinic to successfully treat childhood leukaemia. Of course, one thing has to be noted- when consuming herbs from the garden, do so carefully. Whilst clinical drugs have been tested to determine suitable doses and potential side effects, no data exists regarding the number of leaves it might take to heal or kill. The good news is, for most edible plants, you’d probably have to eat a field’s worth to fall ill. But a leaf or two to spice up dinner and potentially kick that annoying cough you’ve had for weeks- who’s to say no to that?
左手香是一个常见的植物，并享有各种充满诗意的名堂：到手香、过手香、印度琉璃苣、排香草。它起源于东南非洲，是 Lamiaceae 植物家庭的成员。
- Chang JM, Cheng CM, Hung LM, Chung YS, Wu RY. Potential use of Plectranthus amboinicus in the treatment of rheumatoid arthritis. Evidence-Based Complementary and Alternative Medicine. 2010;7(1):115-20