Editor’s note: This article was first published in the July 2017 issue of HerbalEGram, the American Botanical Council’s (ABC’s) monthly e-newsletter. Readers can find the original article, which features eight video clips produced by Chris Kilham, on ABC’s website.

At 85 years of age, Ismail looks fit and strong. The former Malaysian military commando now runs a small farm, overseeing a kesum (Persicaria minor syn. Polygonum minus, Polygonaceae) cultivation program that provides a metric ton (roughly 2,200 pounds) of the fresh herb to local markets every day. Ismail’s wife, Su, is more hands-on, personally working the harvest and keeping watch over other harvesters and the small group of workers who bundle bunches of fresh kesum plants with rubber bands.

This kesum farm is purportedly one of the largest of its kind, just a half-hour drive from Malaysia’s largest city Kuala Lumpur, near the famous Batu caves in Gombak. Kesum requires 90 days to grow to maturity from seed, according to Ismail. The aromatic herb, also known as laksa leaf, is popular in Southeast Asian cookery, loves water, and is best cultivated like rice (Oryza sativa, Poaceae) in paddies. In the case of Ismail’s farm, the paddy is fed by a stream that flows out of a dense rainforest.

It is January 2017, and I am traveling in the company of Nik Fahmi and Tengku Sharir of Biotropics Malaysia, a Malaysian government-owned botanical extraction and marketing company that specializes in plants native to the country. Due to an increased interest in the health benefits of kesum leaves, the government operation has taken an interest in this plant. As we continue our exploration of kesum, various other members of the Biotropics team will join us. Our plan is to investigate this popular savory herb, and to meet with people who understand its broad culinary and medicinal uses. Our visit to the kesum farm kicks off a week of traveling the countryside.

I stoop to pick a couple of leaves of fresh kesum that is one week from harvest. Rolling the leaves between my thumb and forefinger releases aromatic compounds that smell like a blend of oregano (Origanum vulgare, Lamiaceae) and basil (Ocimum basilicum, Lamiaceae), with some other notes mixed in. It is an aroma I recognize from Malaysian, Thai, and Vietnamese dishes. The plant is a slender creeping shrub with climbing branches that stretch 1-1.5 meters (3.3-4.9 feet), and the green leaves are long and lanceolate. In Malaysia and in the US Department of Agriculture’s PLANTS database, kesum is also called pygmy smart weed.¹

After walking through several acres of cultivated kesum, we are led to a large shed where men are bundling kesum into bunches and listening to loud music. The men work quickly, converting large piles of the freshly harvested herb into bunches that will be sold in local markets later that day. The turnaround is fast. Kesum is picked, bundled, trucked to market, and sold fresh.

The leaf of kesum is used in numerous popular dishes in the traditional cuisines of Malaysia, Thailand, Vietnam, and Indonesia. The name “laksa leaf” refers to its use in the traditional spicy noodle soup dish laksa. It is also known in Malaysian cuisine as an ingredient in ulam, or salad, and is eaten finely sliced with other raw vegetables. It is a main ingredient in the mango (Mangifera indica, Anacardiaceae)-based salad kerabu, and is a principal flavor in the rice dish nasi ulam.²

The leaf of kesum is known to contain an array of antioxidant compounds, including flavonoids, aliphatic aldehydes, and phenols, such as rutin, coumaric acid, quercetin, and gallic acid.^3-5 Studies by Baharum et al. detected 48 compounds in the essential oil of kesum using mass spectrometry.⁶ These studies and the work by Vikram et al. provide greater insight into the complexity of the leaves.³

Published chemical analyses and in vitro pharmacological studies suggest that kesum leaves have antibacterial, antifungal, antioxidant, antiviral, cytotoxic, and cytoprotective properties.^2,3

The Forest Research Institute Malaysia (FRIM) in Kepong, Selangor, sits amid 544 hectares (roughly 1,344 acres) of landscaped grounds and verdant forest, and is a brief drive from the center of Kuala Lumpur. Surrounded by Bukit Lagong Forest Reserve, FRIM is Malaysia’s hub for forestry research and conservation. The FRIM herbarium contains more than 350,000 voucher samples that feature the flora of peninsular Malaysia and Sabah. Researchers at FRIM investigate a wide array of plants, from Malaysian trees to food crops endemic to the region, and the center in Selangor oversees research stations in various parts of Malaysia.

At the ethnobotany department of FRIM, researcher Tan Ai Lee shares the latest developments on kesum. The plant is undergoing a name change, we are informed, from Polygonum minus to Persicaria minor. We subsequently confirm this through correspondence with the International Plant Names Index (IPNI). According to IPNI Editor Kanchi Gandhi of Harvard University: “Polygonum minus and Persicaria minor: both are correct names, and it is up to an individual to accept” (email, January 23, 2017).

According to Lee, FRIM has taken the unusual position of developing two kesum-based health product concepts, neither of which was being sold in the marketplace at the time of our visit. We are shown packaging, literature, and product samples. The first, called Kezo Kesum Leaves Seasoning, offers a convenient way to season local dishes with a mixture of dried kesum leaves and sea salt. The second product, called Digesto Digestive Drink, is an “antioxidant digestive beverage.” According to the FRIM literature accompanying this product: “Traditional medicine claims that a decoction of the fresh leaves of kesum is taken as a remedy for indigestion, constipation, flatulence and as a remedy for stomach pains.”

Launching products is a new idea for FRIM, the staff of which has not previously engaged in commercial enterprises of this type. A couple of the staff members there expressed to us that marketing health products was an endeavor far removed from their usual course of work.

Lee said that the FRIM product development program with kesum reflects the high regard with which FRIM researchers assess this traditional herb.  

Traditional Malaysian Medicine Wisdom: A Conversation with Datin Sharifah Anisah

Datin Sharifah Anisah is popularly regarded as an expert on traditional Malaysian medicine, with a focus on women’s health. The subject of numerous articles, Datin Sharifah first provided herb-based therapies and spa treatments in the 1960s. She lectures widely on herbal approaches to health care, has appeared in popular Malaysian publications, and received the Jati Wanita (Teak Women) Award in 2003 from the United Malays National Organization (UMNO).

On a shaded cottage porch at Taman Botani Negara Shah Alam (TBNSA), a botanical garden where visitors can also stay in reconstructed traditional wooden Malaysian houses, Datin Sharifah and I sit to discuss traditional uses of kesum. The location seems perfect for our conversation. TBNSA sports forest acreage, plantations, and gardens.

“In our country, kesum is widely used by Malaysians,” she tells me. “The Malays and the Chinese use it in their food. They believe that kesum is part of health and beauty.”

Datin Sharifah explains that kesum is often added to fish, and that in this manner the herb is a valuable digestive cleansing agent. “We believe that kesum is very good for internal cleansing. It helps for flatulence, you know, ‘wind.’”

According to Datin Sharifah, kesum is often taken as an infusion for medicinal purposes, and is typically mixed with other herbs. “The Malays use it for the internal cleansing, especially for mothers after birth,” she said. “It helps to prevent and overcome postpartum problems.”

From a cosmetic standpoint, she noted that “kesum is often used for the skin, especially for stretch marks.”

For external use, she explained, the kesum leaves are ground into a paste and applied directly to skin. “You make the paste and you add in rice, and sometimes you add in turmeric [Curcuma longa, Zingiberaceae], and sometimes tamarind [Tamarindus indica, Fabaceae] juice. It is very effective to heal the stretch marks.”

Over the course of an hour, Datin Sharifah shared with me various traditional Malaysian approaches to the use of kesum and other herbs, for a broad range of health needs, from relieving indigestion and ulcers to enhancing vaginal health. I noted that her easy manner and broad knowledge of traditional herbal preparations and their uses made Datin Sharifah Anisah a treasure, much in the way that Amazonian shamans are considered “living libraries.” 

Cooking with Kesum: A Discussion with Chef Ismail Ahmad

Malaysia, with its diverse regional cuisines, is not only a foodie paradise, but also a land where excellent chefs can make a reputation for themselves. Among the celebrated chefs in the country, Ismail Ahmad stands out as one of the most beloved and well-known. Flamboyant, funny, creative, and smart, Chef Ismail runs Restaurant Rebung in Kuala Lumpur, a mecca for those who seek authentic Malaysian country food. At noon sharp, when the doors of the restaurant open, a crowd streams in, mostly women in hijab, their destination being the seemingly endless buffet.

Chef Ismail attempts modesty, but all the locals seem to know his celebrity, and patrons of the Restaurant Rebung look for him just to shake his hand and express thanks. Chef Ismail has appeared on the Asian Food Channel, Anthony Bourdain’s “No Reservations,” “Yan Can Cook,” “Aroma,” “Sri Murni,” “Poh’s Kitchen,” “Hey Good Cooking,” “Wok and Roll,” and a number of other food-related television programs.

The food at his restaurant is something to see: the vegetable dishes, soups, salads, various rice preparations, curries of all types, broiled and otherwise prepared fish and meats — every dish offers a different color, texture, and fragrance than the ones around it. There is magic in this cookery, which is aided by the herbs that Ismail grows on the restaurant terrace, and by his upbringing in the Malaysian countryside where he learned about herbs and cookery from his grandmother.

“My grandparents brought me up with organics, things that grow around the garden like pumpkins [Cucurbita pepo, Cucurbitaceae], bananas [Musa spp., Musaceae], cassava [Manihot esculenta, Euphorbiaceae], turmeric, fresh coconut [Cocos nucifera, Arecaceae], and river fishes,” Ismail explains. “It was very rare that we had meat.”

“What were some of the foods that were your favorites when you were a kid?” I ask.

“Oh, I love pumpkin; I love young bananas; oh, I love young jackfruit [Artocarpus heterophyllus, Moraceae]. My grandmother would make curries, you know.”

“Was your grandmother a great cook?”

“She was limited because she did not travel around, but she cooked the best village food.”

Ismail beams when he talks about his grandmother.

On a table before us, Ismail has laid out in bowls all of the ingredients needed to make the mango salad kerabu, which uses a large portion of kesum. “Normally a salad like this we eat when the weather outside is too hot, and we want something fresh and crunchy…. Kesum is my main ingredient. The leaf, you shred it very fine.”

As I watch Ismail perform his culinary magic, he describes every ingredient, and how all the ingredients are put together, as he concocts the salad. When he is done, three women who call themselves “The Fit Ladies of Kuala Lumpur” and I sample the salad. It is savory, citrusy, and fresh. We all pronounce it delicious. One of the Fit Ladies gets a bit teary-eyed, and comments that she hasn’t tasted a dish like this since she was a young girl.

We fly to Kota Bharu, south of Kuala Lumpur in Kelantan state, to visit the legendary Pasar Siti Khadijah, a very large and colorful market run almost entirely by women. The dry market features household goods, knives, brooms, and all manner of general supplies, while the wet market features fish, meat, fruits, vegetables, herbs, and spices. A mezzanine level affords a colorful view of all the food stalls, where a seemingly endless array of fruits, vegetables, and spices are displayed in large piles.

We make our way into the wet market, and immediately spot large piles of kesum stacked at almost every stall. As we stand near one stall, a woman approaches the vendor, and purchases a generous armload of kesum. We follow her upstairs to the restaurant area, and watch her finely chop the pile of kesum for the salads that will be served over the next few hours. She laughs at me as I take her photo. I kid her a bit, and that makes her chop faster. She seems to enjoy the moment.

After observing the food preparation, we purchase a few of the local dishes prepared by women running small stands and restaurants at the Pasar Siti Khadijah. I make sure to order something with kesum: an ulam, an aromatic and tangy salad with other finely-sliced vegetables, hot chiles (Capsicum spp., Solanaceae), salt, and a hint of lime (Citrus hystrix, Rutaceae) — very nice.

Investigating Kesum: An Interview with Annie George, MD

Back in Kuala Lumpur, I sit with Annie George, MD, senior manager of science and clinical trials at Biotropics, where investigation into the properties of kesum has been ongoing for a few years. I asked Annie: “I’m curious to know, of all the herbs you could investigate in Malaysia, what made you choose kesum?”

“Back in the year 2011, we were actually investigating several of the well-known herbs in Malaysia, also looking at the salads consumed by the people, and we tested them for antioxidant activity initially. We found that kesum itself has very high antioxidant values,” she said.

The high antioxidant value of kesum, as determined by standard ORAC* testing, was the first piece of information that set kesum apart from the other herbs being studied.

She continued: “What was very interesting was that it has this quercetin-3-O-glucuronide, and this particular compound has been shown to reduce beta amyloids, and beta amyloids, you find that a lot in patients with Alzheimer’s.”

Annie teamed up with Suzana Shahar, PhD, head of research at the Faculty of Health at the National University of Malaysia (Universiti Kebangsaan Malaysia). Suzana's work focuses on dietary practices that help maintain good health and protect against degenerative diseases. Annie and Suzana thought that kesum seemed like the right candidate for a study on cognition. If it showed activity, it might help the elderly.

The possible cognitive effects of kesum were put to the test in a study of 35 healthy women, half of whom were given a concentrated water extract of kesum (20:1 ratio) daily (BioKesum Biotropics), while the other half received a placebo (maltodextrin). At the beginning of the study, after three weeks, and after six weeks, the subjects participated in a series of psychological and intelligence tests. The kesum extract group scored higher in overall good mood, short-term memory, and IQ. Several parameters of cognitive function also improved. This 2015 study, published in the medical journal Clinical Interventions in Aging, has piqued interest in the popular herb.⁷ Living up to its folk name “smart weed,” kesum appears to act as a nootropic, enhancing cognitive function. Both Annie and Suzana acknowledge that additional studies may bolster this use, but they are happy with the results of this preliminary study.

My week of chasing kesum in Kuala Lumpur and other parts of Malaysia revealed several things. First, I was already familiar with the flavor and aroma of kesum, but didn’t know it yet: The herb was immediately recognizable once I smelled it and put it into my mouth. Second, the fresh herb brightens up dishes and makes a terrific salad ingredient. Finally, the herb is long-established as a traditional remedy, especially for digestive issues, but for others, too. The potential cognitive benefits of kesum, as investigated in the 2015 study, may prove to be consistent with the herb’s “smart weed” moniker.

Considering kesum’s traditional use as a food, its presumed and observed safety, and its various known biological activities, it isn’t a stretch to suggest that it may be smart to consume this herb. 

*ORAC (Oxygen Radical Absorbance Capacity) is an in vitro laboratory assay of the antioxidant value of a substance, and does not necessarily directly relate to the actual antioxidant activity of a substance when ingested by humans.

References

1. Polygonum minus Huds. United States Department of Agriculture Natural Resources Conservation Service website. Available at: https://plants.usda.gov/core/profile?symbol=POMI22. Accessed July 10, 2017.
2. Christapher PV, Parasuraman S, Christina JMA, Asmawi MZ, Vikneswaran M. Review on Polygonum minus. Huds, a commonly used food additive in Southeast Asia. Pharmacognosy Research. 2015;7(1):1-6. doi:10.4103/0974-8490.147125.
3. Vikram P, Chiruvella KK, Ripain IHA, Arifullah M. A recent review on phytochemical constituents and medicinal properties of kesum (Polygonum minus Huds.). Asian Pacific Journal of Tropical Biomedicine. 2014;4(6):430-435. doi:10.12980/APJTB.4.2014C1255.
4. Urones JG, Marcos IS, Pérez BG, Barcala PB. Flavonoids from Polygonum minus. Phytochemistry. 1990;29:3687-3689.
5. Yaacob KB. Kesom oil — a natural source of aliphatic aldehydes. Perfum Flavor. 1987;12:27–30.
6. Baharum SN, Bunawan H, Ghani MA, Mustapha WAW, Noor NM. Analysis of the chemical composition of the essential oil of Polygonum minus Huds. using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC-TOF MS). Molecules. 2010 Oct 12;15(10):7006-7015.
7. Shahar S, Aziz AF, Ismail SNA, et al. The effect of Polygonum minus extract on cognitive and psychosocial parameters according to mood status among middle-aged women: a randomized, double-blind, placebo-controlled study. Clin Interv Aging. 2015 Sep 22;10:15