An ethnobotanical survey of medicinal plants of Laos toward the discovery of bioactive compounds as potential candidates for pharmaceutical development

Abstract

Context: An ethnobotany-based approach in the selection of raw plant materials to study was implemented.

Objective: To acquire raw plant materials using ethnobotanical field interviews as starting point to discover new bioactive compounds from medicinal plants of the Lao People's Democratic Republic.

Methods: Using semi-structured field interviews with healers in the Lao PDR, plant samples were collected, extracted, and bio-assayed to detect bioactivity against cancer, HIV/AIDS, TB, malaria. Plant species demonstrating activity were recollected and the extracts subjected to a bioassay-guided isolation protocol to isolate and identify the active compounds.

Results: Field interviews with 118 healers in 15 of 17 provinces of Lao PDR yielded 753 collections (573 species) with 955 plant samples. Of these 955, 50 extracts demonstrated activity in the anticancer, 10 in the anti-HIV, 30 in the anti-TB, and 52 in the antimalarial assay. Recollection of actives followed by bioassay-guided isolation processes yielded a series of new and known in vitro-active anticancer and antimalarial compounds from 5 species.

Discussion: Laos has a rich biodiversity, harboring an estimated 8000-11,000 species of plants. In a country highly dependent on traditional medicine for its primary health care, this rich plant diversity serves as a major source of their medication.

Conclusions: Ethnobotanical survey has demonstrated the richness of plant-based traditional medicine of Lao PDR, taxonomically and therapeutically. Biological assays of extracts of half of the 955 samples followed by in-depth studies of a number of actives have yielded a series of new bioactive compounds against the diseases of cancer and malaria.

Figure 1

Map of Lao PDR, showing provinces with numbers of healers interviewed (by province). The three numbers separated by a slash indicate the number of healers interviewed, the villages where the interviews took place, and the number of plant species collected. For example: Bolikhamsai Province 24/21/128 = 24 healers interviewed, 21 villages where interviews took place, 128 plant species were collected.

Figure 2

A sample of an interview guide used in the ethnobotanical survey. This particular form is specifically intended for interview on the treatment of MALARIA. Similar forms, each with the disease heading of TUBERCULOSIS, HERPES/COLD SORES, CANCER, respectively, were used for each of those diseases.

Figure 3

A sample of a completed Field Interview Form. This is a sample of a completed Field Interview Data Sheet that has been transcribed from the field notes from an interview session that led to the collection of Gongronema napalense. These data were eventually entered into a NAPIS Database housed at ITM. See text [Results- Ethnobotanical survey- Medicinal plants collected] for details about NAPIS.

Figure 4

Age distribution of the healers interviewed. A total of 118 healers (see Supporting Data #1) in 94 villages, in 15 provinces of Laos, and the Vientiane Prefecture, were interviewed. The age of the healers ranges from 42 to 82, with the majority aged 60–69. Of the 118 healers, only 5 were female.

Figure 5

Statistics on the total number of unique species collected. The high numbers of species from Bolikhamxai (128 species), Champasak (123 species) and Oudomxai (78 species) is partly due to a bias caused by good logistics and good facilities, as well as good communications with healers within the territory of the Traditional Medicine Stations located in these provinces.

Figure 6

Highest frequencies of assay categories (= diseases) across the 15 provinces of Laos. In this histogram, which is a graphic rendition of data in Table 1, the high frequency of occurrence of the highest-scoring disease [= assay] categories in the provinces of Bolikhamsai, Champasak, Oudomxai, Savannakhet, Vientiane, and Xaignabouri are very obvious. For the provinces of Attapeu, Khammouan, Luang Namtha, Luang Prabang, Phongsali, Xekong and Xiangkhoang, due to the small numbers of frequency of occurrence of the disease [= assay] categories, the separation of the bars is not obvious.

Figure 7

Frequency distribution of plant parts of the plant samples collected. The data used to structure this histogram were derived from data in Table 2. The discrepancy (3 plant parts) between the total number of samples (955) and the number of plant parts (952) of the samples collected is due to the fact that the plant parts of three samples were described as “unknown” and have been excluded from the Figure 7 (see text for further details).